Woodworking & lumber calculators

Twelve calculators for framers, deck builders and furniture makers. Type measurements the way you read a tape, and get stair layouts checked against the IRC, deck spans checked against the joist table, and lumber orders down to the board foot.

Lumber

Board Foot CalculatorTally a lumber order in board feet, with price and waste.Cut List CalculatorFit your parts onto stock boards with the fewest boards and least offcut.Plywood CalculatorHow many 4×8 sheets for a wall, floor or roof.Lumber Weight CalculatorWhat a board or a load weighs, by species and moisture.Wood Movement CalculatorHow much a panel will swell and shrink across the seasons.

Stairs

Stair CalculatorRisers, treads, stringer length and angle, checked against the IRC.IRC Stair Code CheckerCheck an existing or planned stair against IRC R311.7 and baluster spacing.

Roof

Roof Pitch CalculatorPitch in x/12, degrees and percent, plus the rafter factor.Rafter CalculatorCommon and hip rafter length, birdsmouth, ridge height and count.

Deck & fence

Deck CalculatorDeck boards, joists, posts, footings, screws and cost.Deck Joist Span CalculatorMaximum joist span and spacing from IRC Table R507.6.Fence CalculatorPosts, rails, pickets and concrete for a wood fence.

Why a 2×4 is 1½" × 3½"

Lumber is named for its size when it comes off the saw, green and rough. It then shrinks as it dries and loses more when the planer surfaces all four sides. Pick a board and walk it through the mill.

2×4 as sold: 1.5" × 3.5"

The dashed outline is the name; the yellow block is the wood you actually get. Since the American Softwood Lumber Standard (PS 20) fixed the dressed sizes, a 2× is 1½" thick and anything 8" and wider loses ¾" of width instead of ½". That's why every calculator here asks for actual dimensions where it matters, and uses nominal size only for board-foot pricing, the way lumberyards do. That preference for real numbers over rounded ones carries over to ahaboo, a site of guided explainers that walk through how things actually work.

About WoodCalc Pro

Are these woodworking calculators free?

Yes. Every calculator is free, needs no account and runs in your browser, so it keeps working on a jobsite with a weak signal once the page has loaded.

Which building code do the stair and deck checks use?

The 2021 International Residential Code (IRC): R311.7 for stairs, R312 for guards and R507 for decks. Many states and cities adopt it with local changes, so confirm with your building department.

Do the calculators take fractions?

Yes. Type measurements the way you read a tape: 7 3/4, 7-3/4, 5' 6" or 66. Results show fractions to the nearest 1/16".

Are my inputs saved?

Each calculator remembers your last inputs in your own browser (localStorage) so you can come back to a job. Nothing is sent to a server except when you press Ask in the "Ask the shop" box. Clear everything on the privacy page.