Hole Spacing Calculator
Achieve accurate hole placement with this powerful hole spacing calculator, the essential tool for machinists, fabricators, and engineers. Instantly compute equal distances for linear, circular bolt patterns (PCD/flange), and square grid layouts with full metric and inches support.
Whether you need center-to-center pitch, edge clearance, mounting alignment, coordinates for CNC programming, or drilled perforation patterns on plate, panel, sheet metal, or wood, this precision calculator delivers accurate measurements, running coordinates, and visual diagrams.
Supports bolt, screw, fastener, anchor layouts, flange circles, slot intervals, and complex spacing for fabrication, machining, structural, and mechanical projects. Includes formulas, diameter checks, and ready-to-use CAD/CNC output to eliminate errors and save time in the machine shop. Perfect for industrial and DIY projects.
Hole Spacing Calculator
Calculate precise hole positions, equal spacing, bolt circle patterns, and grid layouts for drilling, CNC machining, fabrication, and structural engineering projects. Metric & imperial supported.
1. Linear Equal Center-to-Center Spacing
Gives the center-to-center distance between adjacent holes. For equal distribution, all spacings will be identical.
2. Hole Position from Reference (Running Total)
Provides the absolute position of each hole from the starting reference point. Avoids cumulative measurement error.
3. Edge-to-Edge Clearance (between adjacent holes)
4. Minimum Safe Edge Distance
$$k = 1.5 \text{ (non-loaded)}, \quad k = 2.0 \text{ (loaded edge)}$$
Ensures structural integrity. Holes placed closer than this to the material edge risk tearing or crack propagation under load.
5. Circular Bolt Pattern - Angular Step
6. Bolt Circle X/Y Coordinates (CNC-ready)
Cartesian coordinates for each hole, referenced to circle center (0,0). Ready for CNC G-code or CAD import.
7. Chord Length (Adjacent Hole Spacing on Circle)
The straight-line distance between two adjacent holes on the bolt circle. Useful for fitting templates or checking bolt spacing.
8. Grid Layout Coordinates
9. Minimum Center-to-Center Spacing (Structural Check)
Common rule-of-thumb for structural steel per AISC/Eurocode guidelines.
Linear Spacing
Equal hole distribution along any straight line with custom margins
Bolt Circle / PCD
Flanges, wheels, pipe flanges — X/Y coordinates ready for CNC
Grid Layouts
Rows × columns with stagger / brick-offset option
Running Coordinates
Absolute X/Y positions eliminate cumulative error
Edge-Distance Warnings
Auto-flags holes too close to material edges
Engineering Presets
Common flange, wheel bolt patterns pre-loaded
Metric & Imperial
mm, cm, m, inches, feet — switch any time
Visual Diagram
SVG preview scales to any screen — mobile workshop-ready
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Hole Spacing Calculator — Complete User Guide
Step-by-step instructions, all calculation formulas with LaTeX display, annotated SVG diagrams, input parameter reference tables, common mistake guide, and a full FAQ — for drilling, CNC machining, metal fabrication, structural engineering, and woodworking.
What Is a Hole Spacing Calculator?
A hole spacing calculator is a precision layout and engineering tool that automatically computes exact hole positions, center-to-center distances, edge clearances, and X/Y coordinates for holes distributed across any workpiece — a metal plate, structural flange, wooden panel, CNC sheet, mounting bracket, or industrial perforation template.
Instead of measuring hole by hole — a method that compounds small errors into large ones — this online calculator generates accurate, ready-to-use dimensions for drilling, machining, CNC programming, and CAD design. It supports the three fundamental layout patterns used in fabrication:
- Linear (single-row) — Equal hole spacing along a straight centerline
- Circular / Bolt Circle (PCD) — Holes arranged evenly around a pitch circle diameter
- Grid / Matrix — Rows and columns of holes with configurable X/Y pitch
Whether you are a CNC machinist generating bore positions, a structural engineer sizing a base plate, a welder laying out a bolt pattern on a flange, or a woodworker spacing screws on a deck — this calculator eliminates manual math errors and delivers precise, reliable results every time.
Mechanical engineers, metal fabricators, CNC machinists, structural engineers, welders, woodworkers, sheet-metal workers, pipe fitters, automotive technicians, DIY builders — anyone who needs to drill holes accurately and symmetrically in any material: structural steel, aluminium, wood, plastic, or composite panels.
Key User Pain Points & How This Calculator Solves Them
Manual hole layout is one of the most error-prone tasks in fabrication and machining. These are the eight most common problems — and how this calculator eliminates each one.
Cumulative Measurement Error
Measuring from one hole to the next compounds tiny errors. By hole 8, you can be off by several millimetres, causing misalignment or scrapped parts in precision machining.
✓ Fixed: Running totals from a fixed originC-C vs Edge Spacing Confusion
Confusing center-to-center distance with edge-to-edge clearance results in wrongly placed holes. Both values matter in structural and mechanical design.
✓ Fixed: Both values output simultaneouslyBolt Circle Trigonometry
Calculating X/Y coordinates for holes on a circular bolt pattern (PCD) requires trigonometry that is impractical to do reliably on the shop floor.
✓ Fixed: Instant CNC-ready coordinatesWasted Material from Drill Errors
A single misplaced drill hole often means scrapping the entire plate or part — especially in structural steel, aluminium fabrication, or precision CNC projects.
✓ Fixed: Verify layout before drillingMetric vs Imperial Unit Confusion
Mixing metric (mm) and imperial (inches) measurements without careful conversion is a frequent cause of costly drilling errors in global fabrication shops.
✓ Fixed: Built-in mm / cm / in / ft supportEdge Distance Violations
Placing holes too close to the edge of a plate or panel causes tearing and structural failure — a critical issue in bolted steel and anchor connections.
✓ Fixed: Automatic edge-distance warningNo CNC-Ready Output
Manual calculations rarely produce the absolute X/Y coordinates needed for CNC programming or CAD import — requiring double-work by the machinist.
✓ Fixed: Absolute coordinates for all modesNo Visual Preview Before Drilling
Without a diagram, it is impossible to verify a hole pattern before drilling — especially for circular or complex grid layouts on expensive material.
✓ Fixed: Interactive SVG diagram generatedCalculator Modes Overview
Three layout modes, each designed for a specific hole pattern type used in industrial, structural, and workshop projects.
Mode 1 — Linear Hole Spacing
Calculate evenly spaced holes along a straight line with custom edge margins. Solve for spacing, hole count, or total length.
- Center-to-center spacing
- Edge-to-edge clearance
- Running X coordinates from origin
- Structural edge-distance check
Mode 2 — Bolt Circle / PCD
Generate X/Y coordinates for holes around a pitch circle diameter. Used for flanges, wheel hubs, mounting plates, and pipe connections.
- Angle between holes (degrees)
- CNC-ready X/Y coordinates
- Chord (adjacent hole) spacing
- Engineering presets included
Mode 3 — Grid / Matrix Layout
Place holes in rows and columns across a plate or panel. Supports staggered (brick-offset) patterns for perforated sheet and ventilation grilles.
- X/Y coordinate for every hole
- Stagger / row-offset option
- Total plate dimensions calculated
- Scales to 200+ hole layouts
Use Linear for rails, shelf pins, screw strips, and structural connections. Use Bolt Circle for flanges, wheels, pipe fittings, and round mounting plates. Use Grid for perforated sheets, cable trays, ventilation panels, and multi-row CNC drilling programs.
Step-by-Step User Guide
Follow these steps for accurate hole spacing results. Each step explains what to enter and why it matters for precise drill positioning in your fabrication or engineering project.
How to Use the Linear Hole Spacing Calculator
Select Your Solve Mode
Choose what you want the calculator to find. Three options are available:
- Spacing (C-C) — Know length & hole count; find center-to-center spacing.
- Hole Count — Know length & desired spacing; find how many holes fit.
- Total Length — Know count & spacing; find the minimum material length needed.
Enter Total Length / Span
Type the full usable length of your workpiece — the total span available for hole placement. Select your unit (mm, cm, m, inches, or feet) from the dropdown. The unit label is shown beside every input field.
⚠ Common mistake: Entering the outer plate length when you should use the usable drilling zone. Account for clamped ends or unusable sections at either end.
Enter Number of Holes
Input how many holes you need along the span. Minimum is 2 (for a single spacing interval). The calculator handles any quantity — from 2 holes on a small bracket to 50+ on a long structural rail.
⚠ N holes create N−1 spacing intervals. Five holes = four gaps. The calculator applies this automatically — no manual adjustment needed.
Set Start and End Edge Margins
The start margin is the distance from the left material edge to the center of Hole 1. The end margin is the distance from the last hole center to the right edge. Equal margins create a centred, symmetrical layout.
- Structural default: 1.5 × hole diameter minimum
- Loaded bolted connections: 2.0 × hole diameter
- Set both to
0only if no edge constraint applies — the edge-distance warning will flag any violation if a diameter is entered.
Enter Hole Diameter (Recommended)
Entering the hole diameter enables: edge-to-edge clearance output, structural edge-distance warnings, and accurate hole circles in the SVG layout diagram.
⚠ For bolted connections, the drilled hole is typically the fastener diameter + 1–2 mm clearance. Example: an M16 bolt uses a 17–18 mm hole. Enter the drilled hole diameter, not the bolt shank diameter.
Choose Spacing Type & Edge Distance Factor
Select Center-to-Center (CTC) for most structural and mechanical applications — the industry standard. Choose a minimum edge distance factor:
- 1.5 × D — Non-loaded edges (standard default)
- 2.0 × D — Loaded edges, bolted steel connections
- 2.5 × D — Brittle materials, thin panels, plastics
Click Calculate — Review Results
Instant output includes: center-to-center spacing, edge-to-edge clearance, absolute X position of every hole from the start edge, PASS / REVIEW status badge, and an SVG layout diagram with labelled positions.
✓ The coordinate table uses running totals from the reference edge — always measure from the same origin. This is what eliminates cumulative error.
Copy Results for Workshop or CNC Use
Click Copy Results to export a formatted coordinate list to your clipboard. Paste it into your CNC program, CAD drawing note, work order, or inspection sheet.
📋 Workshop tip: Use absolute X positions when marking out on the machine shop floor — never chain-measure from hole to hole.
How to Use the Bolt Circle / PCD Calculator
Enter the Pitch Circle Diameter (PCD / BCD)
The PCD (also called Bolt Circle Diameter) is the diameter of the imaginary circle passing through every bolt hole center. Find it on the engineering drawing, stamped on the flange face, or measure directly opposite holes on an existing part. Enter in mm or inches.
Set Hole Count and Start Angle
Enter the total number of holes and the angular start position of Hole 1. A 90° start angle places Hole 1 at 12 o’clock — the most common convention for pipe flanges and structural bolt patterns.
⚠ When matching an existing pattern, verify the start angle by measuring from the 3 o’clock position (positive X axis) counter-clockwise. A wrong start angle rotates the entire pattern.
Use an Engineering Preset (Optional)
Pre-loaded patterns are available: 4-bolt ⌀150 mm PCD, 6-bolt ⌀200 mm PCD flange, 5-lug wheel (5×114.3 mm), or 6-lug truck wheel (6×139.7 mm). All fields populate automatically when a preset is selected.
Read X/Y Coordinates for CNC / CAD
Results show the angle and exact X/Y coordinates for each hole, referenced to the bolt circle center (0, 0). Enter these directly into AutoCAD, SolidWorks, Fusion 360, or your CNC controller.
⚠ Set your CNC work origin (G54/G55) exactly at the bolt circle center before entering coordinates. A 0.5 mm origin error shifts every hole position by that amount.
How to Use the Grid / Matrix Layout Calculator
Enter Rows, Columns, and Unit
Define the grid size: rows (Y direction) and columns (X direction). A 3×4 grid creates 12 equally spaced holes in a rectangular pattern on your plate or panel. Select the unit for all dimensions.
Enter X and Y Spacing (Pitch)
X spacing = center-to-center horizontal distance (column pitch). Y spacing = center-to-center vertical distance (row pitch). These can differ — asymmetric grids are fully supported.
⚠ Always enter center-to-center (C-C) values, not edge-to-edge. Using the gap between holes instead of C-C distance is the most common grid spacing error.
Set Edge Margins and Stagger Mode
Edge margins control distance from plate edges to outermost hole centers. Stagger modes:
- None — Regular aligned grid
- Row offset — Alternate rows shifted by half X spacing (brick pattern)
- Column offset — Alternate columns shifted by half Y spacing
Review Plate Dimensions and All Coordinates
Results include minimum plate width and height, and an X/Y coordinate for every hole in the grid. Layouts up to 100 holes display in full in the table. Click Copy Results to export any grid size.
Supported Units and Measurements
All standard length units used in metric and imperial engineering, fabrication, and woodworking are supported. The unit symbol is displayed beside every input and output so you always know your active measurement system.
When you change the unit selector, all fields switch to that unit. Never mix metric and imperial in the same calculation. The unit label beside every numeric field tells you which system is currently active.
Unit Conversion Quick Reference
| From | To mm | To Inches | Typical Use |
|---|---|---|---|
| 1 inch (in) | 25.4 mm | — | Imperial fabrication, US steel, wood |
| 1 foot (ft) | 304.8 mm | 12 in | Structural spans, lumber, US building |
| 1 cm | 10 mm | 0.394 in | General workshop reference |
| 1 m | 1000 mm | 39.37 in | Long plates, structural steel, rail |
| 1/4 inch | 6.35 mm | 0.25 in | Common fastener, screw pitch |
| 1/2 inch | 12.7 mm | 0.5 in | Bolt diameter, pipe, bore sizes |
| M8 bolt hole | 9 mm | 0.354 in | Standard metric clearance hole |
| M16 bolt hole | 17–18 mm | 0.67–0.71 in | Structural bolted connections |
All Formulas Used in Hole Spacing Calculations
Every result this calculator produces is based on established engineering mathematics. The complete formula set is shown below with variable definitions and practical notes for each.
Linear Hole Spacing Formulas
Formula 1 — Equal Center-to-Center Spacing
Distributes n holes evenly along a total span. Gives the center-to-center (C-C) distance between any two adjacent holes:
💡 Why n−1? Because n holes create n−1 gaps. Five holes = four spaces. This is the most common source of off-by-one errors in manual layout — handled automatically here.
Formula 2 — Absolute Hole Position (Running Total)
The position of hole i measured from the start reference edge. Absolute positions eliminate cumulative measurement error entirely:
✅ Workshop rule: Always measure from the same datum edge — never from the previous hole. This formula gives you the absolute distance from origin to every hole center.
Formula 3 — Edge-to-Edge Clearance Between Adjacent Holes
The physical air gap between the wall of one hole and the next — critical for checking material web strength:
⚠ If Cete is negative, holes overlap — the layout is geometrically impossible. If Cete < Dhole, the material web may be too thin for structural loads.
Formula 4 — Minimum Safe Edge Distance
The shortest allowable distance from a hole center to the material edge. Violations risk tearing and structural failure under load:
📚 Based on AISC Steel Construction Manual and Eurocode 3, Clause 3.5. Always confirm against the code applicable to your project jurisdiction.
Formula 5 — Solve for Hole Count (Given Desired Spacing)
When you know desired spacing and total length, the maximum number of holes that fit:
Bolt Circle / Circular Pattern Formulas
Formula 6 — Angular Step Between Holes
For n holes equally spaced around a full 360° circle:
📌 6 holes → 60°. 8 holes → 45°. 4 holes → 90°. Always verify this matches your flange drawing specification before drilling.
Formula 7 — X/Y Coordinates for Each Bolt Hole (CNC-Ready)
Cartesian coordinates of each hole, measured from the bolt circle center (0, 0). Enter directly into your CNC machine or CAD system:
⚠ Angles measured counter-clockwise from the positive X axis (3 o’clock) — standard mathematical and CNC convention. Clockwise direction is also selectable.
Formula 8 — Chord Length (Adjacent Hole Spacing on Circle)
The straight-line distance between two adjacent holes on the bolt circle — useful for physical verification with callipers:
Grid Layout Formulas
Formula 9 — Grid Hole Coordinates
X and Y coordinates of each hole in a rectangular grid, measured from the bottom-left corner of the plate:
Formula 10 — Total Plate Dimensions for Grid
Minimum material size needed to contain the full grid with the specified margins:
Formula 11 — Staggered Grid Row Offset
For staggered (brick) patterns, alternate rows are offset by half the column spacing:
📌 A staggered grid achieves a higher open-area percentage than a square grid with the same spacing — useful for ventilation perforation, acoustic panels, and heat-exchanger tube sheets.
Formula 12 — Minimum Structural C-C Spacing (Steel / AISC)
For bolted steel connections, the minimum center-to-center distance between any two holes:
📚 Per AISC Steel Construction Manual and Eurocode 3, Clause 3.5. Verify against the specific code and bolt-size table for your jurisdiction on all structural projects.
Visual Diagrams — Understanding Hole Spacing Concepts
These annotated diagrams illustrate key dimensions, terminology, and spatial relationships for all three calculator modes. Reference them when setting up a drilling template or interpreting results.
Diagram 1 — Linear Hole Spacing: Key Dimensions Explained
Figure 1: Linear hole spacing diagram. Five equally spaced holes on a plate showing all key dimensions: total length (L), start/end margins, center-to-center spacing (Sctc), edge-to-edge clearance gap, and hole diameter (D).
Diagram 2 — Bolt Circle (PCD) Layout: Key Dimensions
Figure 2: Bolt circle (PCD) diagram. 6 equally spaced holes on a 200 mm pitch circle. Key dimensions: radius R, angular step θ, chord length between adjacent holes, and X/Y coordinate axes referenced from center (0, 0).
Diagram 3 — Grid Layout: Rows, Columns, Spacing, and Margins
Figure 3: Grid layout diagram. 3×4 grid (12 holes) with X spacing (Sx), Y spacing (Sy), and X/Y edge margins (mx, my) labelled. All hole coordinates are measured from the bottom-left corner of the plate.
Input Parameters Reference Table
Quick reference for all input parameters, their purpose, valid ranges, and units.
Linear Mode Inputs
| Input Field | What It Means | Valid Range | Unit |
|---|---|---|---|
| Total Length (L) | Full usable span available for hole placement | > 0 | mm / cm / m / in / ft |
| Number of Holes (n) | Total holes to distribute along the span | ≥ 2 (integer) | count |
| Start Margin (mₛ) | Distance from left edge to center of first hole | ≥ 0, < L/2 | same as length |
| End Margin (mᵉ) | Distance from last hole center to right edge | ≥ 0, < L/2 | same as length |
| Hole Diameter (D) | Drilled hole diameter — enables clearance and safety checks | > 0 or blank | same as length |
| Desired Spacing | Target C-C spacing (for hole count / length solve modes) | > 0 | same as length |
| Min Edge Factor (k) | Multiplier for edge distance safety check (1.5, 2.0, or 2.5 × D) | 1.5 / 2.0 / 2.5 | dimensionless |
Bolt Circle Mode Inputs
| Input Field | What It Means | Valid Range | Unit |
|---|---|---|---|
| PCD / BCD | Pitch Circle Diameter — diameter of circle through all hole centers | > 0 | mm / in |
| Number of Holes | Holes distributed evenly around 360° | ≥ 2 (integer) | count |
| Start Angle (θ₀) | Angular position of Hole 1 (0° = 3 o’clock; 90° = 12 o’clock) | 0°–359° | degrees |
| Hole Diameter | Drilled hole size — used for chord clearance check | > 0 or blank | mm / in |
| Direction | CCW (counter-clockwise, standard) or CW (clockwise) | CCW / CW | — |
Grid Mode Inputs
| Input Field | What It Means | Valid Range | Unit |
|---|---|---|---|
| Rows (Nᵣ) | Number of hole rows in Y direction | ≥ 1 (integer) | count |
| Columns (Nᶜ) | Number of hole columns in X direction | ≥ 1 (integer) | count |
| X Spacing (Sₓ) | Center-to-center horizontal column pitch | > 0 | mm / cm / in / ft |
| Y Spacing (Sᵧ) | Center-to-center vertical row pitch | > 0 | mm / cm / in / ft |
| X Edge Margin | Distance from left/right plate edge to outermost hole centers | ≥ 0 | same as length |
| Y Edge Margin | Distance from top/bottom plate edge to outermost hole centers | ≥ 0 | same as length |
| Stagger Mode | None (aligned grid), Row offset (brick pattern), Column offset | 3 options | — |
Common Mistakes & How to Avoid Them
The most frequent errors users make when calculating hole spacing — and the simple corrections that prevent them.
Entering the edge-to-edge gap as the spacing value instead of the center-to-center distance. Results in holes placed too close together and overlapping material warnings.
Always enter center-to-center (C-C) distance as your spacing. The calculator outputs edge-to-edge clearance as a separate result value.
Measuring from the previous hole to the next (chain measurement) when marking out on the workpiece. Compounds errors by the 5th or 6th hole.
Use the absolute X positions from the results table and always measure from the same fixed reference edge on your plate.
Setting start angle to 0° when matching a flange that has the first bolt at 12 o’clock — creating a 90° rotational error in the entire bolt pattern.
Set start angle to 90° for a 12 o’clock first-hole position. Verify the output diagram matches your drawing orientation before drilling.
Entering the hole diameter in inches when the length unit is set to mm — mixing units in the same calculation produces wildly wrong spacing values.
Check the unit label beside every input field before calculating. All values must use the same unit. Convert first if needed.
Setting margins to zero for structural bolted plate connections — placing holes at the raw material edge violates minimum edge distance code requirements.
Apply a minimum margin of at least 1.5 × hole diameter. For loaded bolted connections use 2.0 × D or check the AISC / Eurocode value for your bolt size.
Entering number of holes as 5 when you want 5 spaces — creates 6 holes, making the last hole fall off the end of the plate.
Count actual drill points, not gaps. The calculator automatically computes N−1 spacing intervals from your hole count.
Accuracy and Precision Note
Results Are Mathematically Exact — Physical Accuracy Depends on Your Setup
This calculator applies the exact engineering formulas documented above with full floating-point precision to at least 4 decimal places. The physical accuracy of your drilled holes depends on your measuring tools, drill press or CNC setup, workpiece fixturing, and material properties. Use digital callipers or a height gauge for layout marking. For critical structural or precision machining applications, verify hole positions with a coordinate measuring machine (CMM) after drilling. The minimum edge distance checks in this calculator are based on conservative industry guidelines and must always be confirmed against the applicable engineering code (AISC, Eurocode 3) for your specific project.
All outputs display to 3–4 decimal places. For workshop use, round to the nearest 0.1 mm or to the precision of your measuring instrument. For CNC programming, use the full decimal value — do not round coordinates entered into machine controllers.
Frequently Asked Questions (FAQ)
Answers to the most common questions about hole spacing, bolt circle layouts, and how to apply this calculator to fabrication, machining, and engineering projects.
Center-to-center (C-C) spacing is the distance between the midpoints of two adjacent holes. This is the standard dimension used in engineering drawings, structural codes, and CNC programming. It is independent of hole size.
Edge-to-edge spacing is the physical air gap between the walls of two adjacent holes — the actual clearance between them. It equals C-C spacing minus the hole diameter. This value indicates whether there is enough material between holes to carry structural loads. This calculator outputs both values simultaneously when you enter the hole diameter.
Even number of bolts: Measure center-to-center across two directly opposite holes. That measurement is the PCD directly.
Odd number of bolts (e.g., 5-lug wheel): Measure the chord distance (center-to-center) between any two adjacent holes, then calculate PCD = chord distance ÷ sin(180°/n), where n is the number of holes. Alternatively, enter your measured chord distance and hole count into the bolt circle calculator to find the PCD.
For pipe flanges, the PCD is almost always stamped on the flange face or specified in the manufacturer’s datasheet or piping isometric drawing.
Yes — the calculator is fully suitable for wood and timber projects. The linear and grid modes are ideal for shelf pin holes, dowel spacing, deck screw patterns, cabinet mounting rails, stair baluster holes, and furniture fastener layouts. Use inches or mm as appropriate. The edge distance warnings are based on steel fabrication rules; for wood, a practical minimum edge clearance is 1.5–2× the screw or dowel diameter from any edge.
Linear mode: X positions are absolute distances from the left edge (your datum). Set CNC X zero at the plate’s left edge and enter each X value as an absolute G90 move in a G81 canned drilling cycle.
Bolt circle mode: All X/Y coordinates reference the bolt circle center. Set your CNC work offset (G54) exactly at the bolt circle center, then enter each X/Y pair as an absolute position for a G81 cycle.
Grid mode: Coordinates reference the bottom-left corner of the plate. Set your work zero at the plate’s bottom-left corner and use X/Y pairs for each hole. Click “Copy Results” to export all coordinates as plain text.
The minimum edge distance is the shortest allowable distance from the center of a hole to the nearest edge of the steel plate. Standards:
- AISC (USA): Minimum edge distance ranges from 1.25× to 1.75× bolt diameter depending on bolt size and edge type (sheared or rolled). Preferred minimum is often stated as 1.5× D for standard connections.
- Eurocode 3 (EU): Minimum end distance e₁ ≥ 1.2 d₀; minimum edge distance e₂ ≥ 1.2 d₀, where d₀ is the hole diameter (not the bolt diameter).
This calculator uses a simplified k×D check (1.5, 2.0, or 2.5) as a conservative guide. Always verify against the specific code clause and bolt-size table for structural projects.
Set the start margin to your required value and the end margin to 0 (or vice versa). The formula S = (L − mₛ − mᵉ) / (n−1) still applies with mᵉ = 0, meaning the last hole sits at the far end of the usable length. This is useful for rail-mounted systems where holes must align with a fixed reference at one end only.
A staggered pattern offsets alternate rows by half the column spacing so holes in Row 2 sit between the holes in Row 1 rather than directly below them. Common uses include:
- Perforated metal sheets for ventilation and acoustic panels
- Cable tray and grating manufacture
- Heat exchanger tube sheets (triangular pitch)
- Any application needing higher open-area percentage while maintaining web strength
A staggered grid with the same pitch as a square grid achieves approximately 15.5% more open area, which improves airflow and drainage without weakening the material between holes in any single row.
Yes. For square hollow sections (SHS), rectangular hollow sections (RHS), or circular tube/pipe, enter the usable face length as your total length, set your margins to keep holes away from the section corners or welds, and the resulting hole positions apply directly to the face you are drilling. The edge distance check will help you avoid placing holes too close to section corners, which is a common failure point in hollow section connections.
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