Steel Hardness Conversion Calculator | HB, HRC, HV, HRB + Tensile Strength

Free online steel hardness conversion calculator. Convert between HB, HRC, HRB, HRA, HV, HLD, BHN and estimate tensile strength. ASTM E140 based.

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Published - February 28, 2026
Updated - June 21, 2026

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Comparing hardness values across different testing scales shouldn't slow your workflow. This free steel hardness conversion calculator converts between HB, HRC, HRB, HRA, HV, HLD, and BHN in seconds, with tensile strength estimation built in. Powered by ASTM E140 interpolation tables, it handles carbon steel, alloy steel, and stainless steel with range validation and formula transparency. Whether you're a machinist, metallurgist, or QA engineer, get reliable reference-grade results without flipping through printed charts.

⚙️ Steel Hardness Conversion Calculator

Convert HB · HRC · HRB · HRA · HV · HLD · BHN instantly — with Tensile Strength estimation. ASTM E140 / ISO 18265 based.

ASTM E140 ISO 18265 7 Scales Tensile Strength Free Tool

🔢

Section 1 — Interactive Multi-Scale Hardness Calculator

▼

Input Scale

Hardness Value Valid range: HRC 20–70

Material Type

Condition

💪

Section 2 — Tensile Strength Converter

▼

Hardness Scale

Hardness Value

Material

Tensile Strength

Unit

Material

UTS Estimation Formulas for Steels

The following empirical correlations are widely accepted in metallurgical practice (ASTM, ISO):

$$\text{From Brinell (HB):} \quad UTS_{MPa} \approx 3.45 \times HB$$ $$\text{From Vickers (HV):} \quad UTS_{MPa} \approx 3.3 \times HV$$ $$\text{From Rockwell C (HRC):} \quad UTS_{MPa} \approx 3.45 \times HB(HRC)$$ $$\text{Yield Strength (approx):} \quad YS \approx 0.6\text{–}0.9 \times UTS$$ $$\text{Note: Accuracy} \approx \pm 5\%\text{; for critical use, direct testing is required.}$$

📊

Section 3 — Complete Steel Hardness Conversion Table

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HRC (Rockwell C)	HRB (Rockwell B)	HRA (Rockwell A)	HB (Brinell)	HV (Vickers)	HLD (Leeb)	UTS MPa (Steel)	UTS ksi

ℹ️ Table data based on ASTM E140-12b (Standard Hardness Conversion Tables for Metals — Carbon and Alloy Steels). Values are for carbon and alloy steel in the annealed/tempered condition.

🏗️

Section 4 — Steel-Specific Hardness Notes

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🟠 Carbon Steel

Most common steel; ASTM E140 tables apply directly
Typical annealed range: HRC 10–25 / HB 150–270
Fully hardened (high-C): HRC 60–67 / HV 700–900
Formula: UTS ≈ 3.45 × HB applies accurately
Beware: case-hardened surfaces read higher than core
Machinability index drops sharply above HRC 40

🔵 Alloy Steel

Includes Cr, Mo, Ni, V alloying elements
Standard ASTM E140 tables remain applicable
Higher hardenability allows deep through-hardening
Typical heat-treated range: HRC 25–55 / HV 260–600
Tool steels may reach HRC 60–65
Tensile correlation still valid (±8%)

🟢 Stainless Steel

Austenitic (304, 316): Not hardenable by heat treatment; use HRB or HV
Martensitic (410, 420): Hardened to HRC 40–58; ASTM E140 applicable
Duplex: Moderate hardness HRB 90–100 / HV 220–280
Note: Tensile correlation is less accurate for austenitic grades
Vickers (HV) is preferred for thin stainless sections

⚠️ Important Conversion Limitations

Conversions are for homogeneous materials only — case-hardened surfaces behave differently
HRB scale limited to relatively soft materials (HRB 60–100); do not use for hardened steels
Brinell (HB) not suitable above ~650 HB due to ball indenter deformation
All conversions carry an inherent ±3–5% uncertainty due to material microstructure variability
For certification and quality control, always use direct testing on the target material

❓

Section 5 — Frequently Asked Questions

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Need More Precision?

For critical applications, always supplement calculator results with direct hardness testing on your actual material sample. This tool provides ASTM-based approximations for reference and engineering estimation.

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⚙ Complete User Guide & Formula Reference

Steel Hardness Conversion Calculator
— How It Works & All Formulas Explained

A step-by-step guide covering every hardness scale, every formula, input validation rules, accuracy limitations, and common conversion mistakes — for engineers, metallurgists, and machinists.

ASTM E140 ISO 18265 HB · HRC · HV · HRB · HRA · HLD Tensile Strength 7 Scales Covered

Section 01

What the Steel Hardness Conversion Calculator Does

The Steel Hardness Conversion Calculator converts a hardness value measured on one scale into equivalent values across all other major hardness scales — simultaneously. It also estimates the material's Ultimate Tensile Strength (UTS) from hardness, a critical value for material selection and design.

Rather than manually looking up printed ASTM E140 conversion tables and interpolating between rows, this tool performs table-based linear interpolation automatically — giving you engineering-grade results in seconds.

"A hardness conversion calculator doesn't just save time — it eliminates the human interpolation errors that cause part failures when the wrong material is specified."

— ASTM E140 Hardness Conversion Standard, Background Note

What It Calculates and Outputs

Output	Unit / Scale	Method	Applies To
HRC — Rockwell C	HRC	ASTM E140 interpolation	Hardened steels
HRB — Rockwell B	HRB	ASTM E140 interpolation	Soft steels, annealed
HRA — Rockwell A	HRA	ASTM E140 interpolation	Thin hardened parts
HB / BHN — Brinell	HB	ASTM E140 interpolation	Cast iron, steels
HV — Vickers	HV	ASTM E140 interpolation	All metals, thin coatings
HLD — Leeb (Rebound)	HLD	ASTM E140 interpolation	Portable testing, large parts
UTS — Tensile Strength	MPa / ksi	Empirical formula (3.45 × HB)	Carbon & alloy steels only

Section 02

Step-by-Step User Guide: How to Use the Hardness Converter

Select Your Input Hardness Scale

In the "Input Scale" dropdown, choose the scale your hardness tester uses or the scale listed on your material certificate. Options: HRC, HRB, HRA, HB, HV, HLD. The valid range hint below the value field will update automatically when you change the scale.

💡 Not sure which scale you have? HRC and HRB are most common. If your number is between 20–70, it's likely HRC. If it's between 60–105, it may be HRB. If it's between 100–800, it's probably HB (Brinell). See Section 3 for a full scale guide.

Enter Your Hardness Value

Type your measured hardness number into the "Hardness Value" field. Decimals are accepted (e.g., 45.5 HRC). The field turns green if the value is within the valid range for that scale, or red if it falls outside the accepted range.

⚠️ Common mistake: Entering an HRB value (e.g., 95) into the HRC field. HRC 95 does not exist — the maximum is HRC 70. If your input turns red, double-check which scale you're using.

Choose Material Type

Select the material from the "Material Type" dropdown: Carbon / Alloy Steel, Stainless Steel, Aluminum, Cast Iron, or Copper Alloys. This affects the tensile strength coefficient used in the UTS calculation. The ASTM E140 hardness conversion table values remain the same for all steel types — material selection only changes the UTS formula factor.

⚠️ Common mistake: Selecting "Carbon Steel" for austenitic stainless steel (304/316). These materials cannot be hardened by heat treatment, and their hardness-to-tensile correlation is different. Choose "Stainless Steel" for accurate tensile estimates.

Select Hardening Condition

Choose from Through-Hardened, Case-Hardened, or Annealed / Soft. This is a reference field that helps interpret your results — case-hardened surfaces have a higher hardness than the core, so conversions apply only to the surface layer measured.

🚨 Critical note for case-hardened parts: A Brinell test on a case-hardened part may average the hard surface and soft core, giving a misleading result. Use Vickers (HV) or Rockwell (HRC) for case-hardened surfaces — these indenters are shallow enough to stay within the hardened layer.

Click "Convert Now" and Read Results

Press ⚡ Convert Now. Results appear as cards showing the equivalent value in each scale plus estimated tensile strength. The input scale card is highlighted in red to confirm your source. Cards showing N/A mean that value falls outside the conversion table's valid range for that scale.

✅ Click the ⧉ copy icon on any individual result card to copy just that value, or use "📋 Copy All Results" to copy all conversions as formatted text for pasting into a report or email.

Review the Formula Display

Below the results, a Formula box shows exactly which calculation method was used — confirming that ASTM E140-12b linear interpolation and the UTS approximation formula were applied. This provides traceability for engineering reports.

📐 MathJax renders the formulas in LaTeX notation. If formulas appear as raw text, your browser may have blocked the MathJax script. Try refreshing or enabling scripts for the page.

Use the Conversion Table (Section 3 of Calculator)

The full ASTM E140 reference table is available in Section 3 of the calculator. Filter by HRC value to jump to the relevant row. Download as .csv for use in Excel, or use the print button for a paper copy to keep at your testing station.

Section 03

Steel Hardness Scales Explained: HRC, HRB, HRA, HB, HV, HLD

Each hardness scale uses a different indenter geometry, applied load, and measurement principle. Understanding these differences prevents scale confusion — the most common source of conversion errors.

Scale	Full Name	Indenter	Load	Valid Range	Best For
HRC	Rockwell C	120° Diamond Cone (Brale)	150 kgf	20 – 70	Hardened & tempered steels, tool steels
HRB	Rockwell B	1/16″ Steel Ball	100 kgf	60 – 105	Soft steels, annealed alloys, aluminum
HRA	Rockwell A	120° Diamond Cone	60 kgf	60 – 88	Cemented carbides, thin hard coatings
HB / BHN	Brinell (HBW)	10 mm Tungsten Carbide Ball	3000 kgf	100 – 650	Cast iron, coarse-grained steels, forgings
HV	Vickers (HV / VPN)	136° Diamond Pyramid	1–100 kgf	100 – 1500	Thin materials, coatings, all metals; widest range
HLD	Leeb / Rebound (D-type)	3 mm Tungsten Carbide Ball	Dynamic impact	300 – 900	Portable in-field testing, large workpieces

ℹ️ HB vs BHN vs HBW: These three terms refer to the same test. BHN = Brinell Hardness Number (legacy term). HB = Brinell Hardness (general). HBW = Brinell Hardness with Tungsten carbide ball (current preferred notation per ASTM/ISO). The calculator treats all three as identical.

Section 04

All Hardness Conversion Formulas Used in Results Calculation

The calculator uses ASTM E140-12b linear table interpolation as its primary conversion engine — not a single formula. This is the most accurate method available. Below, we also document the empirical formulas for reference and the internal conversion helpers used for scales not directly in the master table.

"Hardness conversions are empirical relationships, not physical laws. No single formula is universally accurate across all materials and conditions."

— ASTM E140-12b, Section 1.4 — Scope and Limitations

Primary Method: ASTM E140 Linear Interpolation

For a given input value (e.g., HRC 45), the calculator finds the two nearest rows in the ASTM E140 reference table — one above (A) and one below (B) — and interpolates all other scale values proportionally.

Linear Interpolation Formula — ASTM E140 Table Method

$$t = \frac{V_A - V_{input}}{V_A - V_B}$$ $$X_{output} = X_A - t \times (X_A - X_B)$$

Where V = source scale value, X = target scale value, A = row above input, B = row below input. t = interpolation factor (0 = exactly at row A, 1 = exactly at row B).

Empirical Approximation Formulas (for Reference)

These formulas appear in engineering textbooks and standards. The calculator uses table interpolation for higher accuracy, but these formulas are useful for quick mental estimates and are documented here for full transparency.

HRC → HB (Brinell)

$$HB \approx 8.34 \times HRC + 100$$

Valid range: HRC 20–65. Accuracy ±5%. For steel only.

HV → HRC (Rockwell C)

$$HRC \approx \frac{HV - 100}{8.34}$$

Valid range: HV 240–900. Simplified inverse of HRC→HB→HV chain.

HB → HV (Vickers)

$$HV \approx \frac{HB}{0.9544}$$

Valid up to ~400 HV. Deviation increases at higher values.

HV → HB (Brinell)

$$HB \approx 0.9544 \times HV$$

Best accuracy below 400 HV. Used internally by UTS estimator.

HRC → HV (Vickers)

$$HV \approx 104.7 \div (130 - HRC)$$

Empirical formula. Valid HRC 20–65. Use ASTM table for precision.

HB → HRC (Rockwell C)

$$HRC \approx \frac{HB - 100}{8.34}$$

Inverse of HRC→HB approximation. Valid HB 190–740.

HRB → HB (Brinell)

$$HB \approx 130 - \frac{430}{HRB}$$

Simplified approximation. Valid HRB 60–100 for soft steels.

HRA → HRC (Rockwell C)

$$HRC \approx 2 \times HRA - 104$$

Valid HRA 70–88. Direct linear fit from ASTM E140 table data.

🎯 Which method does the calculator actually use? Always ASTM E140 linear interpolation — not the approximate formulas above. The formulas are shown here for your reference and to explain the underlying relationships. The table interpolation gives ±3% accuracy vs ±5–8% for the shortcut formulas.

Section 05

Tensile Strength Estimation Formulas: Hardness to UTS (MPa, ksi, psi)

The correlation between hardness and Ultimate Tensile Strength (UTS) is one of the most useful relationships in materials engineering. It allows tensile strength to be estimated non-destructively from a simple hardness test — saving time and material.

Formula 1 — UTS from Brinell Hardness (HB) for Steel

The most widely accepted formula, derived from empirical testing of carbon and alloy steels across a broad hardness range. Accurate to approximately ±7%.

UTS from HB — Carbon & Alloy Steels (ASTM / SAE J417)

$$UTS_{MPa} \approx 3.45 \times HB$$ $$UTS_{ksi} \approx 0.5 \times HB$$ $$UTS_{psi} \approx 500 \times HB$$

Example: HB 300 → UTS ≈ 3.45 × 300 = 1035 MPa ≈ 150 ksi. Valid range: HB 100–400. Accuracy ±7% for carbon/alloy steel. Not valid for austenitic stainless, aluminum, or copper alloys.

Formula 2 — UTS from Vickers Hardness (HV) for Steel

UTS from HV — Steel (Empirical)

$$UTS_{MPa} \approx 3.3 \times HV$$

Example: HV 350 → UTS ≈ 3.3 × 350 = 1155 MPa. Valid HV 100–700. Derived from HV ≈ HB / 0.9544, substituted into HB formula.

Formula 3 — UTS from Rockwell C (HRC) for Steel

There is no single linear formula from HRC to UTS. The calculator first converts HRC → HB via ASTM E140 interpolation, then applies the HB formula.

UTS from HRC — Two-Step Method

$$HB = f(HRC) \quad \text{[ASTM E140 table interpolation]}$$ $$UTS_{MPa} \approx 3.45 \times HB$$

Example: HRC 45 → ASTM table → HB ≈ 421 → UTS ≈ 3.45 × 421 = 1452 MPa.

Material-Specific Tensile Strength Coefficients

Material	UTS Formula	Coefficient (k)	Accuracy	Notes
Carbon Steel	UTS = 3.45 × HB	3.45	±5–7%	Most reliable correlation; broad data set
Stainless Steel	UTS = 3.30 × HB	3.30	±10–12%	Less accurate for austenitic grades; use direct testing
Aluminum Alloys	UTS = 3.30 × HB	3.30	±10–15%	Wide variation between alloys; for estimation only
Copper Alloys	UTS = 4.50 × HB	4.50	±10%	Higher coefficient due to copper's ductility
Cast Iron	Direct formula correlation unreliable — cast iron has low ductility and high variability. Use direct tensile testing.

Reverse Lookup: Tensile Strength → Hardness

The calculator also performs the reverse: enter a tensile strength in MPa, ksi, or psi, and it estimates the equivalent hardness values.

Reverse Lookup — Tensile → Hardness

$$HB \approx \frac{UTS_{MPa}}{3.45}$$ $$HV \approx \frac{UTS_{MPa}}{3.3}$$

Unit conversions used internally: 1 ksi = 6.895 MPa · 1 psi = 0.006895 MPa · 1 MPa = 145.038 psi. HRC is found by inverse lookup in the ASTM E140 HB column.

Yield Strength Estimation

Estimated Yield Strength (YS)

$$YS \approx 0.6 \text{ to } 0.9 \times UTS$$ $$\text{Calculator uses: } YS_{est} \approx 0.7 \times UTS$$

The ratio YS/UTS varies by alloy and temper condition. 0.7 is a commonly used average for quenched-and-tempered steels. Always verify with actual tensile test data for structural applications.

Section 06

Input Validation Rules: Valid Ranges for Each Hardness Scale

The calculator validates your input in real time. Understanding these rules helps you enter data correctly and interpret warning messages.

Valid — field turns green, conversion proceeds

Invalid — field turns red, results may be unreliable

Warning shown — value accepted but flagged as approximate

Scale	Min Valid	Max Valid	What Happens If Out of Range	Common Input Errors
`HRC`	20	70	Red field + warning banner; results shown but labeled unreliable	Entering HRB values (80–105) in HRC field; entering raw Brinell (200–400)
`HRB`	60	105	Red field + warning; do not use HRB above HRB 105 — material is too hard	Entering Vickers (HV) values — HV 200 looks like HRB 200, but HRB max is 105
`HRA`	60	88	Red field; range is narrow — HRA mostly used for cemented carbides	Confusing HRA with HRC — HRA 70 is a completely different material than HRC 70
`HB`	100	740	Red field; Brinell ball deforms above ~650 HB causing inaccurate indentations	Entering HV value — Vickers and Brinell values diverge significantly above 400
`HV`	100	940	Red field above 940 HV — table data ends; extrapolation not performed	Entering load-qualified values like "HV10 = 450" — enter only the number 450
`HLD`	300	900	Red field; Leeb scale is instrument-specific — values below 300 indicate very soft materials beyond table coverage	Confusing HLD (D-impact device) with HLC or HLS — each device gives different numbers

🚨 Most common mistake: Entering the wrong scale. A Brinell hardness of 200 HB entered as HRC would flag as valid (HRC 20–70 range) but produce completely wrong conversions. Always verify your scale before clicking Convert.

Section 07

Accuracy, Error Limits & Why Hardness Conversions Are Approximate

🎯 Accuracy Statement — Build Trust in Your Results

Hardness conversions are empirical correlations, not exact physical equations. They are derived by testing large batches of steels and fitting equations to the resulting data. This means every conversion carries an inherent uncertainty. Understanding this uncertainty is essential for engineering decision-making.

ASTM Table Method

±3–5%

Typical error for carbon & alloy steel

Approximate Formulas

±5–8%

Single-equation estimates

UTS Estimation

±7–10%

Hardness → tensile strength

Stainless / Al / Cu

±10–15%

Non-steel materials

Why Are Conversions Approximate?

Microstructure variation: Two steels with identical chemical composition but different heat treatment history will have different hardness-to-tensile relationships.
Test conditions: Surface roughness, specimen thickness, indentation location, and operator technique all affect the measured hardness number.
Scale design differences: HRC measures indentation depth; HV measures indentation area. These are fundamentally different physical quantities being correlated statistically.
Material composition range: ASTM E140 tables cover a wide range of carbon and alloy steels. The more your specific alloy deviates from this average, the higher the conversion error.
Range proximity: Conversions near the top or bottom of a scale's valid range are less accurate than conversions in the middle of the range.

When to Trust the Conversion — and When to Test Directly

Use Case	Conversion Suitable?	Recommendation
Material selection / specification comparison	✓ Yes	Conversion results are sufficient for preliminary selection
Cross-referencing supplier certificates	✓ Yes	Use conversion to verify ballpark equivalence between scales
Engineering estimation of tensile strength	~ Approx	Acceptable for early-stage design; add safety factor of ≥1.5
QC acceptance / rejection of parts	✗ No	Perform direct hardness test using the specified scale
Structural / safety-critical design	✗ No	Require certified tensile test results (coupon or certificate)
Certification / compliance documentation	✗ No	Conversions are not accepted as substitute for direct testing by most standards

Section 08

Common Hardness Conversion Mistakes — and How to Avoid Them

These are the most frequent errors users make when performing hardness conversions. Each includes a microcopy tip explaining how to avoid it.

#	Mistake	Example of Error	Correct Approach	Risk Level
01	Using the wrong input scale	Entering `200 HB` as `HRC 200`	Always verify the scale on your hardness tester printout or certificate before entering	Critical
02	Converting outside valid range	Trying to get HRB for a hardened steel at HRC 60	HRB maxes out at ~HRB 105 (≈HRC 5). Above HRC 22, HRB readings are invalid. Use HRC or HV for hard steel.	High
03	Applying steel UTS formula to aluminum	UTS = 3.45 × HB used for 6061 aluminum	Select "Aluminum Alloys" in Material Type — the calculator uses a different coefficient. Still approximate: direct tensile testing is recommended.	High
04	Converting case-hardened surface with Brinell	HBW test on carburized gear tooth, entering result for core hardness	Brinell ball is too large — it measures both surface and core. Use HRC or HV (microhardness) for case-hardened parts. Select "Case-Hardened" in the condition dropdown as a reminder.	Critical
05	Treating "N/A" as zero	Seeing N/A in HRB result for HRC 60 material and assuming HRB = 0	N/A means the conversion is outside the valid range for that scale — not that the hardness is zero. The material is simply too hard to be measured with HRB.	Medium
06	Including load qualifier in the input field	Entering `450` for `HV10 450` — this is correct; entering `HV10` as text — this causes an error	Enter only the numeric value. The load qualifier (HV1, HV10, HV30) is important for microhardness but is handled by the scale selector, not the value field.	Low
07	Confusing HLD device types	Using HLC (C-type) readings as HLD input	HLD, HLC, HLS, HLG are different impact devices giving different numbers for the same material. This calculator uses HLD (D-type, most common). Convert your device reading to HLD first using the instrument's built-in conversion, or use a Leeb instrument that outputs HLD directly.	Medium
08	Using UTS estimate for structural design without safety factor	Designing to UTS = 1000 MPa because the calculator returned that value	Always apply a design safety factor of ≥1.5 to estimated (not measured) tensile strength values. The ±10% formula error plus real-world variability means the actual UTS could be 900 MPa or 1100 MPa.	Critical

Section 09

Hardness Scale Range Visual Reference Chart

This chart shows the valid measurement range of each hardness scale on a normalised scale, helping you quickly identify which scale is appropriate for your material's expected hardness range.

Fig. 1 — Valid hardness ranges for each scale, mapped to approximate Brinell equivalent. Vickers (HV) covers the widest range; HRB covers only the soft end. Overlapping regions allow multi-scale conversions; gaps indicate where a scale is not suitable.

📌 Key takeaway from the chart: HV (Vickers) is the only scale that spans nearly the full hardness range of steel — from soft annealed (HV 100) to maximum carburised surface hardness (HV 940). If you need one universal scale, use HV.

Section 10

Quick Reference: Common Steel Hardness Benchmarks Across All Scales

Use this table to quickly verify a conversion or cross-check a certificate value. Values are taken directly from ASTM E140-12b Table 1 for carbon and alloy steels.

Material Condition	HRC	HRB	HB (BHN)	HV	UTS (MPa)	UTS (ksi)
Fully hardened high-C steel (e.g. D2, W1)	65	—	688	832	2374	344
Hardened tool steel (e.g. H13, M2)	60	—	614	746	2118	307
Hardened bearing steel (52100)	58	—	587	706	2025	294
Heat-treated alloy steel (4140, 4340)	45	—	421	481	1452	211
Medium-hard alloy steel	35	—	327	370	1128	164
Normalised medium carbon steel (1045)	22	97	257	272	886	128
Annealed medium carbon steel (1020)	10	95	195	209	672	97
Soft annealed low carbon steel (1010, A36)	0	89	159	170	549	80

📋 The full 34-row ASTM E140 reference table (HRC 0 to 68, with HRB, HRA, HB, HV, HLD, UTS MPa, and UTS ksi columns) is available in Section 3 of the calculator — download it as a CSV for use in Excel or print it for your testing workstation.

Cheat Sheet: Formula Summary Card

Primary Method

ASTM E140-12b table interpolation
Linear between two nearest table rows
Used for ALL scale-to-scale conversions
Accuracy: ±3–5%

UTS Formulas

UTS(MPa) = 3.45 × HB (steel)
UTS(MPa) = 3.30 × HV (steel)
UTS(ksi) = 0.50 × HB
YS ≈ 0.70 × UTS

Quick Approx Formulas

HB ≈ 8.34×HRC + 100
HV ≈ HB ÷ 0.9544
HRC ≈ (HV−100) ÷ 8.34
HRC ≈ 2×HRA − 104

Unit Conversions

1 ksi = 6.895 MPa
1 MPa = 0.145 ksi
1 psi = 0.006895 MPa
1 N/mm² = 1 MPa