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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.
Paint needed by room size (8-ft walls, two coats)
Walls only, with doors and windows left in; rounded up to whole gallons. When you are just over a gallon line, a quart usually covers the difference.
| Room | Wall area | Exact gallons | Gallons to buy |
|---|---|---|---|
| 10 × 10 ft | 320 sq ft | 1.8 | 2 |
| 12 × 12 ft | 384 sq ft | 2.2 | 3 |
| 12 × 14 ft | 416 sq ft | 2.4 | 3 |
| 14 × 16 ft | 480 sq ft | 2.7 | 3 |
| 16 × 20 ft | 576 sq ft | 3.3 | 4 |
| 20 × 20 ft | 640 sq ft | 3.7 | 4 |
What 1, 2, and 5 gallons of paint cover
| Paint | One coat, smooth walls | Two coats, smooth walls | Two coats, textured walls |
|---|---|---|---|
| 1 gallon | 350 sq ft | 175 sq ft | 125–150 sq ft |
| 2 gallons | 700 sq ft | 350 sq ft | 250–300 sq ft |
| 5 gallons | 1,750 sq ft | 875 sq ft | 625–750 sq ft |
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.
How much paint do I need for a 12×12 room?
With 8-ft walls, a 12×12 room has 48 ft of wall and 384 sq ft of wall area. Two coats at 350 sq ft per gallon is 2.2 gallons. Subtract a door and two windows (about 50 sq ft) and it drops to 1.9 — so 2 gallons will do, with 3 only if you leave the openings in.
How much paint do I need for a 10×10 room?
About 2 gallons. Four 10-ft walls at 8 ft tall are 320 sq ft; two coats is 640 sq ft of coverage, or 1.8 gallons at 350 sq ft per gallon. Add the ceiling separately with the ceiling paint calculator.
Should I buy a 5-gallon bucket or single gallons?
Once you need more than about 3–4 gallons of one color, a 5-gallon bucket is usually cheaper per gallon and guarantees one consistent batch. If you buy separate gallons, mix them together in a bucket before you start so the color doesn’t shift between walls.
Does primer count as a coat of paint?
No. Primer is a separate step with its own coverage, so estimate it with the primer calculator and enter only your finish coats here. A tinted primer can let you make a big color change in two finish coats instead of three.