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PaintingPaint Calculator — How Much Paint Do I Need?
Add up the length of every wall you’re painting, enter the ceiling height and number of coats, and get the gallons to buy. Based on about 350 sq ft of coverage per gallon.
How this calculator works
We multiply total wall length by height for wall area, multiply by the number of coats, then divide by 350 sq ft — typical coverage for one gallon on primed, smooth walls — and round up to whole gallons.
What changes how much you need
- Coverage drops on rough, textured, or porous surfaces — figure about 250–300 sq ft per gallon.
- Big color changes (dark to light, or bold colors) often need an extra coat or a tinted primer.
- This estimate doesn’t subtract doors and windows, which leaves a small buffer for touch-ups.
- Buy all your paint in one batch so the color lot matches.
Frequently asked questions
How much does a gallon of paint cover?
About 350–400 sq ft per coat on smooth, primed walls. Textured or unprimed surfaces can drop to 250–300 sq ft.
How many coats of paint do I need?
Two is standard for an even finish. One can work when repainting a similar color; three may be needed for dramatic color changes.
Should I subtract doors and windows?
For a quick estimate you don’t have to — leaving them in builds a small surplus for touch-ups. For large openings, subtract about 20 sq ft per door and 15 per window.