About BuildMath
BuildMath is a set of free calculators for people who need to know how much material to buy for a US home project, in feet and inches.
The BuildMath team
US home-project calculatorsThe BuildMath team writes and maintains these calculators. We turn tape-measure sizes into cubic yards, tons, bags, and tile counts, keep the formulas in the open, and publish a worked example next to each answer.
Why the site exists
Most homeowners are not trying to become estimators. They have a 10 × 20 driveway or a 10 × 12 bathroom and need a number they can take to a yard or a tile aisle. Other tools often hide waste inside the only figure on the page, count bags from the wrong yield, or open in meters. BuildMath keeps US units first, shows the raw quantity and the order quantity as separate lines, and names the density or bag size it used.
There are no accounts and no database. The site is static. Your inputs live in the page URL so you can send someone the same job.
How we check our math
Every formula lives in a TypeScript function, not in the page layout. Each function has unit tests with known answers: a 10 × 20 ft area at 4 inches is 2.47 cubic yards of gravel; a 10 × 12 ft room of 12 × 12 in tile with 10% waste is 132 tiles. Those cases come from independent arithmetic, then we compare the page to them. Densities and bag sizes are listed as typical values you can edit. Price fields stay empty until you type a supplier quote, or until we have a sourced typical US range.
The full checklist is on the methodology page.
Last reviewed October 22, 2026.
How to report a correction
Found a mistake in a result? Email hello@buildmathhq.com with the page link, or use the contact page. The link includes your inputs, so we can see exactly what you entered.