About Easy Wood Calc

Easy Wood Calc is a set of free calculators for woodworking and lumber projects: board feet, nominal and actual lumber sizes, plywood and deck boards, deck joist spans, stair stringers, deck balusters, wall studs and rafters, miter and crown molding angles, finish coverage, firewood and log scaling. Each one shows the formula it uses, so you can check the math yourself or do it on the back of a board at the lumberyard.

The numbers are planning estimates. Wood is a natural material — its density, stiffness and movement vary from board to board — and lumberyards, codes and product labels all have their own rules. Where a value is a typical figure rather than a fixed one, the page says so and names the source it comes from, listed under “Sources” on each calculator. Building codes are adopted and amended locally, so for structural work such as stairs, decks and railings, your building department has the final word.

It is part of a small family of free project calculators that began with Easy Scale Calc (opens in a new tab). The site is supported by advertising and by Amazon affiliate links on product recommendations; neither changes what the calculators say. If you spot an error or want a calculator added, the contact page is the place to say so.

How we build and check the calculators

• Every calculator runs entirely in your browser — nothing you type is sent anywhere.
• Each page shows its formula, and every result shows the working with your own numbers, so you can check it by hand.
• Lumber is handled at its real size — a 2×4 is 1½ × 3½ in — and board, sheet and piece counts are rounded up, with waste allowances shown and editable.
• Where a result depends on a building code (stairs, guards, spans), we use the IRC sections linked on each page; tables are transcribed cell by cell and compared with the official text. Your local building code and inspector have the final say.
• Every calculator is tested in both US and metric units, and every worked example is recomputed at build time so the numbers on the page always match the calculator.

How this content is made

The calculators, worked examples and guides on this site were drafted with the help of AI tools and then checked in several passes. Every number on a worked-example page is recomputed from the calculator at build time, so the text and the calculator can’t disagree. Formulas and published figures (building-code tables, manufacturer data sheets, extension-service rates) are checked against the linked sources, and structural tables are transcribed cell by cell and compared with the official text.

Automated checks run on every build: each calculator is tested in US and metric units and unit switching must round-trip exactly. If you find an error, tell us — corrections are fixed and logged below.

Sources we use

• International Code Council — 2021 International Residential Code, Chapter 3 (R311.7 stairways, R312 guards) (opens in a new tab) — stair riser, tread, headroom and guard limits
• International Code Council — 2021 International Residential Code, Chapter 5 (R507 decks) (opens in a new tab) — Table R507.6 deck joist spans, Table R507.7 decking
• International Code Council — 2021 International Residential Code, Chapter 6 (R602 wall framing) (opens in a new tab)
• International Code Council — 2021 International Residential Code, Chapter 8 (R802 roof framing) (opens in a new tab)
• American Wood Council — DCA 6, Prescriptive Residential Wood Deck Construction Guide (opens in a new tab) — deck joist span definitions and a cross-check of the span values
• USDA Forest Products Laboratory — Wood Handbook: Wood as an Engineering Material (FPL-GTR-282, 2021) (opens in a new tab) — density, stiffness, shrinkage and moisture figures; finishing
• NIST — PS 20-20 American Softwood Lumber Standard (Revision 1, 2021) (opens in a new tab) — nominal and dressed lumber sizes, board measure
• American Hardwood Export Council — The illustrated guide to American hardwood lumber grades (opens in a new tab) — board feet, surface measure and quarter (4/4) thicknesses
• Virginia Cooperative Extension 420-085 — Forest Landowner’s Guide to the Measurement of Timber and Logs (opens in a new tab) — Doyle, Scribner and International log rules
• California Department of Food and Agriculture, Division of Measurement Standards — Firewood (opens in a new tab) — the 128 cu ft cord and how firewood may be sold
• APA – The Engineered Wood Association — Panel Design Specification (opens in a new tab) — approximate plywood and OSB panel weights
• The Wood Database (Eric Meier) (opens in a new tab) — species density, hardness and shrinkage

How the site is funded

Easy Wood Calc is free and has no sign-up. It is supported by display advertising and by affiliate links — when you buy something through a product link we may earn a small commission at no extra cost to you. Recommendations are chosen for fit with the job, not commission.

Corrections

Spotted a wrong number or an unclear explanation? Tell us — corrections are fixed quickly and logged here.

No corrections logged yet.