Paint Calculator
Free paint calculator to estimate gallons and liters from wall area, coverage rate, coats, and waste.
Results
3Gallons to buy
- 2.51Exact gallons
- 11.36Liters (approx.)
How it works
Gallons = (area × coats × (1 + waste%)) ÷ coverage per gallon. We round up so you buy enough cans.
Worked example
Example: 400 sq ft of walls, 350 sq ft/gal coverage, 2 coats, 10% waste → about 2.51 gallons exact, so buy 3 gallons (≈11.4 L).
How to measure wall area
Measure each wall’s height and width in feet, multiply for square footage, then add the walls together. Subtract large openings such as doors (~20 sq ft) and windows if you want a tighter estimate. For ceilings, use length × width of the room.
Coverage rates and coats
Most interior paints cover about 350–400 sq ft per gallon on a smooth surface. Rough or porous walls need more. Dark-to-light color changes often need a primer plus two finish coats. Check the can label for the manufacturer’s coverage.
Why add waste
A 10% waste allowance covers spills, touch-ups, and roller absorption. Bump to 15% for textured walls or intricate trim. Leftover paint is useful for later repairs.
Frequently asked questions
How much paint do I need for a 12×12 room?
A 12×12 room with 8 ft ceilings has roughly 384 sq ft of wall area (excluding doors/windows). At 350 sq ft/gal with 2 coats and 10% waste, plan on about 3 gallons.
Should I count doors and windows?
Yes for accuracy. Subtract their area from the total wall square footage, or keep a smaller waste % if you already measured openings out.
Is this paint calculator free?
Yes. YardCalc’s paint calculator is free to use with no signup. Results are estimates—always verify coverage on the product label.
How do I convert paint gallons to liters?
Multiply gallons by 3.785. YardCalc shows both gallons to buy and an approximate liter equivalent so you can compare US and metric cans.
How much paint per square foot?
Coverage is usually listed as square feet per gallon (often ~350–400 on smooth walls). Invert that for gallons per square foot, then multiply by coats and waste using this paint calculator.
Estimates only. Verify coverage rates and local requirements before purchasing materials. Not a substitute for professional advice.