Determine the minimum lumber size for floor joists based on span, spacing, and load. Calculations follow the NDS using bending stress, deflection (L/360 live, L/240 total), and shear checks.
Project Inputs
IRC 2021: 40 psf minimum for most living areas
Enter your project inputs and click Calculate
All Sizes — Utilisation
Size
Bending
LL Deflection
TL Deflection
Result
Governing Design Check —
⚠ Disclaimer
This tool provides preliminary estimates for informational purposes only. Results are based on simplified NDS calculations and do not replace a formal structural engineering review. All designs must be verified by a licensed structural engineer before construction. Local building codes may impose additional requirements.
