About & methodology

Lumber Calculator builds calculators for woodworking and building projects. Each tool shows the formula it uses so you can check the math yourself.

Data sources

Wood density and hardness: USDA Forest Products Laboratory, Wood Handbook: Wood as an Engineering Material, and published Janka side-hardness values. Densities are approximate at ~12% moisture content.
Stairs: 2021 International Residential Code (IRC) section R311.7, and the American Wood Council's Prescriptive Residential Wood Deck Construction Guide (DCA 6) for cut stringers.
Lumber prices: typical US retail ranges for surfaced stock, compiled from hardwood dealer price lists. Last reviewed October 2026; reviewed quarterly. Regional prices vary 20–40%.

Found an error in a formula or a table? Tell us and we'll fix it and note the change.