Paint Calculator
Work out how many gallons of paint you need from your room size, number of doors and windows, and coats — using the standard 350 sq ft per gallon coverage rate painters estimate with.
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You might also need:Drywall Calculator·Tile Calculator
How paint quantities are estimated
gallons = (area × coats) ÷ 350
Paint coverage is quoted per gallon per coat — 350 sq ft is the realistic planning figure for smooth interior walls (the 400 on the can assumes ideal conditions). Rough texture, bare drywall and dramatic color changes push consumption up 20–30%.
Coverage by surface type
| Surface | Coverage per gallon |
|---|---|
| Smooth, previously painted wall | 350–400 sq ft |
| Lightly textured wall | 300–350 sq ft |
| Heavy texture / popcorn ceiling | 250–300 sq ft |
| Bare drywall (first coat) | 250–300 sq ft |
| Rough masonry / stucco | 150–250 sq ft |
Buying smart
- Round to quarts when close: if you need 2.2 gallons, buy 2 gallons + 1 quart rather than a third gallon.
- Box your gallons: mix all cans of the same color together in one bucket so slight tint variations never show mid-wall.
- Keep 10% for touch-ups: label the can with the room and date. A quart of leftover matched paint saves a full repaint later.
- Painting new drywall? Count the sheets first with the drywall calculator.
Frequently asked questions
How much does a gallon of paint cover?+
One gallon covers about 350–400 square feet with one coat on a smooth, previously painted wall. Textured, porous or bare surfaces absorb more — plan on 250–300 square feet per gallon for those.
How many coats of paint do I need?+
Two coats is the standard for a uniform, durable finish. One coat can work when repainting with the same color. Going light over dark (or covering red/deep colors) may take three coats — or one coat of tinted primer plus two of finish.
How much paint do I need for a 12x12 room?+
A 12 × 12 ft room with 8-foot ceilings has about 384 sq ft of wall area. Subtracting a door and two windows leaves ~330 sq ft, so two coats needs about 2 gallons of wall paint. The ceiling adds 144 sq ft — roughly another half gallon per coat.
Do I need primer?+
Prime bare drywall, patched areas, stains, glossy surfaces, and any drastic color change. Modern paint-and-primer-in-one products handle color refreshes fine, but they don’t replace a dedicated primer on new or problem surfaces.
How much paint do doors and windows subtract?+
The standard estimating allowance is 20 square feet per door and 15 square feet per window. This calculator subtracts them automatically from your wall area.