Cold-Formed Steel Design Calculator
Free cold-formed steel (CFS) design calculator: section properties, axial/flexural capacity, web crippling, and screw connections.
SteelSolver.com
Cold-Formed Steel (CFS) Design Calculator
Size and check light-gauge steel studs, tracks, headers, and connections — section properties, axial & flexural capacity, web crippling, and screw connections, per AISI S100 or AS/NZS 4600.
Engineering note: This tool uses simplified, closed-form approximations of the AISI S100 / AS-NZS 4600 provisions for quick, preliminary sizing. It is not a substitute for full Direct Strength / Finite Strip analysis software or review and stamping by a licensed engineer. Always verify governing checks before construction.
Section geometry
33 mil ≈ 0.0329 in · 43 mil ≈ 0.0428 in · 54 mil ≈ 0.0538 in · 68 mil ≈ 0.0677 in
Formulas used (thin-wall centerline method)
\[ A = t \sum L_i \qquad I_x = \sum \left( \frac{L_i^3 \sin^2\theta_i}{12} + L_i\, d_i^2 \right) t \qquad S_x = \frac{I_x}{y_{max}} \qquad r_x = \sqrt{I_x / A} \]
Centerline lengths \(L_i\) for web, flanges, and lips; \(d_i\)= distance of each element's centroid from the section centroid. Corner-radius effects are neglected in this simplified tool (flat-width centerline approximation) — a small conservative/unconservative shift versus full AISI Table B1 properties.
Section & material
Tip: calculate a section in Tab 1, then re-enter its Ag / Ix / Sx / rx / ry here — or overwrite with your own catalog values.
Bracing & unbraced lengths
Applied loads (demand)
Axial capacity — Direct Strength Method (simplified)
\[ F_e = \frac{\pi^2 E}{(KL/r)^2} \qquad \lambda_c = \sqrt{F_y/F_e} \]
\[ F_n = \begin{cases} 0.658^{\lambda_c^2}\,F_y & \lambda_c \le 1.5 \\ \dfrac{0.877}{\lambda_c^2}\,F_y & \lambda_c > 1.5 \end{cases} \qquad P_{ne}=A_g F_n \]
\[ P_n = \min(P_{ne},\,P_{nl},\,P_{nd}) \]
\(P_{nl}\) (local) and \(P_{nd}\) (distortional) are estimated here from approximate plate-buckling coefficients for a lipped-channel flange/lip assembly. Full designs should confirm these with finite-strip software (e.g. CUFSM).
Flexural & shear capacity
\[ M_n = S_e\,F_y \qquad V_n = A_w F_v,\ \ F_v = \min(0.6F_y,\ \text{shear-buckling limit}) \]
Combined axial + bending (AISI H1.2, simplified)
\[ \frac{P}{P_n/\Omega\ \text{or}\ \phi P_n} + \frac{M}{M_n/\Omega\ \text{or}\ \phi M_n} \le 1.0 \]
Web crippling / bearing check
Formula — AISI S100 Section G (single unstiffened web)
\[ P_n = C\,t^2 F_y \sin\theta \left(1 - C_R\sqrt{R/t}\right)\left(1 + C_N\sqrt{N/t}\right)\left(1 - C_h\sqrt{h/t}\right) \]
Coefficients \(C, C_R, C_N, C_h\) depend on the loading condition selected above and are built into this calculator per AISI S100 Table G2-1 for single-web, unstiffened-flange sections. Stiffened flanges, multi-web (box/back-to-back) sections, and combined bending+crippling interaction require additional checks beyond this simplified module.
Screw connection capacity
Formulas — AISI S100 Section E4 (approximate)
\[ P_{ns,\,shear} = \min\Big(4.2\sqrt{t_2^{3}d}\,F_{u2},\ \ 2.7\,t_1 d\,F_{u1},\ \ 2.7\,t_2 d\,F_{u2}\Big) \]
\[ P_{n,\,pullout} = 0.85\,t_2\,d\,F_{u2} \qquad P_{n,\,pullover} = 1.5\,t_1\,d_w\,F_{u1} \]
These are simplified representations of the AISI bearing/tilting, pull-out, and pull-over equations for self-drilling screws. Actual capacities also depend on thread engagement, screw shear strength (manufacturer catalog value), and edge distance / spacing minimums — check those separately.
Project info
More CFS & structural tools on SteelSolver.com
Working on a different part of the design? Jump to a related calculator:
