Paint Calculator
Estimate the amount of paint needed for walls, rooms, or other flat surfaces. Enter your measurements, number of coats, paint coverage, and optional paint price to receive a practical purchase estimate.
Results
Enter your measurements to see an estimate.
Calculated: — EasyBuildTools, www.easybuildtools.com
How to use the undefined
Pick a calculation mode. Rectangular room measures all four walls automatically from the room length and width. Individual wall is best for a single accent wall or an odd-shaped space you measure wall by wall. Custom total area lets you enter a paintable area you already know.
- Choose your measurement system (feet or meters).
- Enter the room or wall dimensions and the wall height.
- Add the number of doors and windows so their area is subtracted.
- Set the number of coats, the coverage printed on your paint can, and a waste allowance.
- Optionally add a price per gallon and enable primer.
Results update automatically as you type. Use Copy Results to paste the estimate into a note or shopping list, or Print Results for a clean paper copy at the store.
Formula and methodology
The calculator follows standard painting math:
- Gross wall area = total wall length × wall height. For a room, total length is 2 × (length + width).
- Openings = (doors × door width × door height) + (windows × window width × window height).
- Net paintable area = gross area − openings (never below zero).
- Coated area = net area × number of coats.
- Adjusted area = coated area × (1 + waste% / 100).
- Exact gallons = adjusted area ÷ coverage per gallon.
The purchase recommendation converts exact gallons into cans, treating 1 gallon as 4 quarts. It rounds up to whole quarts, then rolls 4 quarts into a gallon — so 2.3 gallons becomes "2 gallons and 2 quarts." Cost multiplies the recommended can volume by your price per gallon.
Worked example
Room: 12 ft × 14 ft with 8 ft ceilings, one standard door (3 ft × 6.7 ft), two windows (3 ft × 4 ft), two coats, 350 sq ft/gal coverage, 10% waste.
Total wall length = 2 × (12 + 14) = 52 ft. Gross area = 52 × 8 = 416 sq ft. Door = 20.1 sq ft; windows = 24 sq ft; openings = 44.1 sq ft. Net = 371.9 sq ft. Two coats = 743.8 sq ft. With 10% waste = 818.2 sq ft. Exact = 818.2 ÷ 350 = 2.34 gallons, so buy 2 gallons and 2 quarts. Enter these values above to confirm.
Helpful measurement tips
- Measure each wall at its longest point and round up to the nearest few inches.
- Only subtract large openings. Very small windows barely change the result.
- Textured, porous, or dark-to-light color changes soak up more paint — treat coverage as a maximum, not a promise.
- Keep a little extra for touch-ups, and record the color and finish for future matching.