About MyDeckMath

MyDeckMath is a collection of free deck calculators built for one simple reason: figuring out how much lumber, concrete and hardware a deck needs shouldn't take an evening with a spreadsheet.

Every calculator on this site shows its work. The formula, the step-by-step math with your own numbers substituted in, and the assumptions behind the defaults are printed right below the result — so you can check the answer against your supplier's quote instead of trusting a number in a black box.

The calculators cover the whole deck build: material takeoff, boards, composite decking, joists and spans, fasteners, railings, stairs, footings, stain and paint, plus the converters that turn areas into linear feet and board feet. The homepage calculator gives you a full takeoff from a single set of dimensions.

How we source our numbers

Reference values come from published standards: joist spans follow IRC 2021 Table R507.5 for Southern Pine #2 with 40 psf live and 10 psf dead load; board foot math follows the NHLA rule; lumber dimensions use actual dressed sizes (a 5/4×6 deck board is 5.5 inches wide). Material prices and coverage rates are national planning averages, clearly labeled as estimates — always confirm prices with your local yard.

What we don't do

No accounts, no tracking walls, no ads in the calculator, no invented statistics or fake reviews. The tools work in your browser and the pages are built to load fast on a phone in a lumber yard parking lot.

Found a mistake or a number that doesn't match your local code? Get in touch — corrections are welcome at the contact page.