About Dollar Math Home

Dollar Math Home builds free, fast calculators for home improvement and DIY projects: how much paint, flooring, tile, concrete, mulch, gravel, drywall or shingles to buy, how to lay out stairs and what size air conditioner a room needs. It is part of Dollar Math, which also makes free paycheck, mortgage, loan and tax calculators.

Where our numbers come from. Our formulas are standard geometry. Coverage rates and rules of thumb (paint per gallon, concrete bag yields, shingles per square, thinset and grout coverage, joint compound per sheet) come from manufacturer guidance and common trade practice. Building code figures come from the International Residential Code (IRC). Air conditioner sizing follows the ENERGY STAR room air conditioner chart.

Your privacy. All calculations run in your own browser. We never receive the numbers you enter.

Limits. Our calculators give estimates for common situations. Products vary, so always check the coverage printed on what you buy, and follow your local building code. For structural work, get advice from a licensed contractor or engineer.

Spotted a mistake or want a new calculator? Tell us on our contact page.