Square footage formulas
For a rectangle, multiply length by width. For a triangle, multiply base by height and divide by two. For a circle, square the radius and multiply by pi. Use quantity to total several identical rooms or areas.
Using the result
Square footage is the starting point for paint, flooring, tile, roofing, sod, and many other material estimates. Add the waste allowance in the specific project calculator.
Related calculators
Frequently asked questions
Should I add extra material?
Yes. Most projects need an allowance for cuts, breakage, uneven surfaces, overlap, or measurement error. The appropriate percentage depends on the material and layout.
Can I use this estimate to place an order?
Use it to plan and compare costs, then verify package coverage and project requirements with the manufacturer, supplier, or qualified contractor before a large purchase.