Use this free paint calculator to work out how much paint a room or wall needs before you buy. Enter the paintable area, the number of coats, and the coverage on your paint can, and this tool shows the paint needed in gallons and liters, plus how many whole cans to buy — no sign-up, no account, and no personal information needed. Your numbers are calculated in your browser and are not sent to us.
Contents: Formula · How to use · Examples · Tips · FAQ · Related tools
No sign-up required. This tool works in your browser, so the amounts you enter are not stored or sent to us. Always check the coverage printed on your paint can, because it varies by brand, surface, and whether you are painting a smooth wall or a rough surface.
Paint Calculator Formula
The calculation is the same in imperial and metric units. First, multiply the paintable area by the number of coats. Then divide by the coverage of one gallon or one liter. Finally, round up to the next whole can, because you cannot buy part of a can.
Total area to cover = Paintable area × Number of coats
Paint needed = Total area to cover ÷ Coverage per gallon or liter
Cans to buy = Round up (Paint needed)
For example, 400 square feet with 2 coats gives 800 square feet to cover. At 350 square feet per gallon, that is 800 ÷ 350 = 2.29 gallons, so you buy 3 gallons. In liters, 2.29 gallons × 3.785 = 8.66 liters.
How to Use the Paint Calculator
Choose square feet and gallons, or square meters and liters, to match your paint can. Enter the total paintable area — for one wall, that is its length times its height; for a room, add the walls together and subtract large doors and windows if you want a closer figure. Enter the number of coats, usually 2 for a color change, and the coverage from your can, often about 350 square feet per gallon or 10 square meters per liter. Tap Calculate Paint, and the result shows gallons, liters, and whole cans together.
If your can gives coverage in a different unit, change the unit choice first, then enter that figure. Do not guess the coverage: a primer, a dark color over a light wall, or a rough surface can all change how far a can goes.
Paint Calculator Examples
Example 1 — 400 square feet, 2 coats, 350 square feet per gallon. Total = 400 × 2 = 800. Paint = 800 ÷ 350 = 2.29 gallons (8.66 liters). Buy 3 gallons.
Example 2 — 100 square meters, 2 coats, 10 square meters per liter. Total = 100 × 2 = 200. Paint = 200 ÷ 10 = 20.00 liters (5.28 gallons). Buy 20 liters.
Example 3 — One room wall, 12 feet by 8 feet, 1 coat, 350 square feet per gallon. Area = 12 × 8 = 96 square feet. Paint = 96 ÷ 350 = 0.27 gallons (1.04 liters). Buy 1 gallon, and keep the rest for touch-ups.
Paint Calculator Tips
Buy a little extra for touch-ups, especially for a color you may need to match later. For background on paint coverage, see Wikipedia's article on paint. Paint in good light, stir the paint well, and use a primer when you change from a dark color to a light one — primer is cheaper than extra top coats. Measure each wall separately rather than guessing the total, and remember that ceilings, trim, and doors are usually painted separately from walls.
Paint Calculator FAQ
How many coats do I need? Two coats are normal for a color change or a new wall. One coat may be enough for the same color in good condition.
What coverage should I use? Use the figure on your paint can. A common guide is about 350 square feet per gallon, or about 10 square meters per liter, but it varies by brand and surface.
Should I subtract doors and windows? Yes, for a closer estimate. Subtract large doors and windows from the wall area, but keep a small allowance for touch-ups.
Does this tool include primer? No. Run the calculation again with the primer's coverage if you need primer, because primer and topcoat are bought separately.
How do I measure a room for paint? Add the lengths of all the walls, multiply by the ceiling height for the wall area, then subtract large doors and windows if you want a closer figure.
Related Tools
Try the Tile Calculator for floors, the Concrete Calculator for slabs, the Meters to Feet converter, and the Ratio Calculator. Return to the PDGPT homepage to browse all free calculators by category.