Calculators
Paint Coverage Calculator
Calculate how many gallons of paint a room needs from wall area, doors, windows, ceiling, coats and coverage per gallon.
- Runs in your browser
- Nothing uploaded
The tool
Enter your numbers below. Results update as you type, and nothing leaves your browser.
Everything you enter stays on your own machine. Nothing is sent to us or to anyone else, which you can confirm in your browser network tab.
What people use it for
- Buying paint for a room
- Estimating a whole-house repaint
- Pricing a painting job
- Comparing paint brands by coverage
About this tool
What the Paint Coverage Calculator does
Paint is bought by the gallon or litre, and each can covers a stated area per coat. Work out the wall area, subtract doors and windows, add the ceiling if you are painting it, multiply by the number of coats and divide by the coverage. Rough or porous surfaces need more.
It also works as a interior paint estimator or a how much paint do I need calculator.
Formula
- Wall area = perimeter × height − doors × 20 sq ft − windows × 15 sq ft
- Gallons = (wall area + ceiling) × coats ÷ coverage per gallon
Worked example
Using the starting values in the calculator above:
| Input | Value |
|---|---|
| Room perimeter | 50 ft |
| Wall height | 8 ft |
| Doors | 2 |
| Windows | 3 |
| Ceiling area (0 if not painting) | 0 sq ft |
| Coats | 2 |
| Coverage per gallon | 350 sq ft |
| Result | Value |
|---|---|
| Gallons to buy | 2 |
| Exact gallons needed | 1.80 |
| Litres | 6.8 |
| Paintable area | 315 |
How to read the result
New drywall, strong colour changes and textured walls often need a primer coat and lower coverage than the label states.
Buying all the paint in one batch avoids slight colour differences between cans.
Quantities are estimates. Check product data sheets and local codes, and confirm with your supplier before ordering.
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Questions
Questions about this tool
The things clients actually want to know — costs, timelines, ownership and what happens after launch.
Typically 350 to 400 sq ft per coat on smooth, primed walls.
Usually yes for an even finish, especially with colour changes.
About 2 gallons for two coats on 8 ft walls, excluding the ceiling.
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