Know what to buy before you go to the store
Free calculators for paint, flooring, roofing, concrete, fences and lumber. Every result shows the formula, the assumptions and the sources, so you can check the math yourself.
- 12 free calculators
- Formula and sources on every page
- No sign-up, no email
12 × 12 ft room, 8 ft walls, 2 coats
2.10 gallons
Buy 2 gallons + 1 quart
| Wall area | 384 sq ft |
| Doors and windows | −50 sq ft |
| Paintable area | 334 sq ft |
Pick your project
Each calculator turns a few tape-measure readings into the amount to buy.
Gallons and quarts of paint for walls and ceilings.
Boxes of flooring and tile, waste included.
Roofing squares, shingle bundles and pitch.
Cubic yards, bags and tons of gravel.
Posts, rails, pickets and deck boards.
Board feet and drywall sheets.
Most used calculators
Each card shows the calculator's answer for a typical project.
How Matholio works
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Measure the space
Length, width and height in feet. Each calculator shows a diagram of what to measure.
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Enter your numbers
The estimate updates as you type, with each step of the math listed under it.
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Buy the right amount
Quantities come rounded to the cans, bags, boxes and boards that stores actually sell.
Built on published numbers
Default values come from manufacturer data and industry guidance, and every calculator lists its sources. You can change any assumption to match the product you buy.
Sources cited across our calculators
- Sherwin-Williams
- Benjamin Moore
- Bob Vila
- GAF
- Quikrete
- Lowe's