Paint Calculator
Find out how much paint you need for a room.
How to Calculate How Much Paint You Need
- Enter your room's length, width, and wall height.
- Enter how many doors and windows are on the walls (their area is subtracted automatically).
- Choose how many coats of paint you plan to apply.
- See the total paint needed in gallons or liters, updated instantly.
Frequently Asked Questions
How much wall area does a gallon of paint cover?
This calculator assumes about 350 square feet per gallon (roughly 32.5 square meters, or about 10 square meters per liter), a commonly cited average for one coat of standard interior paint. Actual coverage varies by paint brand, wall texture, and application method — check your specific paint can for its stated coverage.
Why does it subtract doors and windows?
Doors and windows aren't painted the same as walls, so their area is subtracted from the total wall area before calculating how much paint you need — otherwise you'd overestimate and could overbuy.
Why would I need more than one coat?
A single coat often doesn't fully hide the previous wall color, especially with a big color change (like going from dark to light) — two coats is standard practice for full, even coverage, which is why the tool multiplies your paint needed by the number of coats you select.
Is my data sent anywhere?
No — the calculation happens entirely in your browser using JavaScript, so nothing you enter is ever sent to a server.