Paint Calculator
Estimate paint needed (gallons or liters) from wall area, coats, and coverage rate. Subtract doors and windows for a pre
Room Dimensions
Paint Requirements
Paint Needed
2 coats • buy 2 gal + 1 qt
Wall Area
Paintable wall surface
Primer Needed
Base coat coverage
Project Cost
Total Cost
$0.49 per sq ft
Project Timeline
Paint Selection Guide
How it works
A paint calculator estimates how much paint a job needs by dividing the surface area by the paint's coverage rate (about 350 square feet per gallon), then multiplying by the number of coats. Subtract large openings like doors and windows.
Paint needed
Gallons = (wall area ÷ coverage) × coats
- wall area
- total ft² to paint (minus doors/windows)
- coverage
- ≈ 350 ft² per gallon
- coats
- usually 2
Worked example
- Walls total 700 sq ft
- Coverage 350 ft²/gallon, 2 coats
- Gallons = (700 ÷ 350) × 2
≈ 4 gallons for two coats.
Good to know
- Coverage drops on rough, porous, or unprimed surfaces — round up.
- A dark-to-light color change usually needs an extra coat or a tinted primer.
- Buy a little extra from the same batch for touch-ups so the color matches.
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Frequently Asked Questions
How much paint do I need for a room?
Divide the paintable wall area by the paint's coverage rate (about 350 square feet per gallon) and multiply by the number of coats. A typical 12 x 12 foot room with 8-foot ceilings needs roughly 2 gallons for two coats on the walls.
How do I calculate wall area for painting?
Multiply the room's perimeter by the ceiling height, then subtract openings — about 21 square feet per door and 15 square feet per average window. Only subtract large openings; small fixtures aren't worth deducting.
How many coats of paint do I need?
Two coats is the standard for an even, durable finish. Going from a dark color to a light one, or painting new drywall, usually calls for a tinted primer or an extra coat.
How many square feet does a gallon of paint cover?
Most paints cover 250-400 square feet per gallon, with 350 as a common planning number. Rough, porous, or unprimed surfaces absorb more paint, so use the low end of the range for textured walls or bare wood.
Should I buy extra paint?
Yes — order about 10% extra from the same batch number so touch-ups match exactly. Leftover paint also lets you repair scuffs years later without color-matching a faded wall.