Paint Calculator
Enter your wall area and the number of coats. One gallon covers about 350 ft² per coat. The calculator subtracts nothing for doors and windows by default — adjust the area if you have large openings.
Updated · How we calculate
Your measurements
2 coats suits most repaints. Use 3 for bare drywall or to cover a dark color with a light one; 1 only for a same-color refresh.
Paint needed
3 gal
How the cans get used
- Applied to walls2.29 gal
- Spare in cans0.71 gal
Estimates only. Verify against your supplier's coverage figures before ordering.
Footprint
Wall & coats
400 ft² × 2 coats · 3 gal to buy
Coverage
- Wall area
- 400 ft²
- Coats
- 2 coats
How much paint for common rooms
| Room | Size | Paint needed |
|---|---|---|
| Bathroom walls | 5 × 8 ft room, 8 ft ceiling (208 ft² of wall) | 2 gal |
| Bedroom walls | 12 × 12 ft room, 8 ft ceiling (384 ft² of wall) | 3 gal |
| Bedroom ceiling | 12 × 12 ft (144 ft²) | 1 gal |
| Living room walls | 15 × 20 ft room, 8 ft ceiling (560 ft² of wall) | 4 gal |
| Large open room walls | 20 × 30 ft room, 9 ft ceiling (900 ft² of wall) | 6 gal |
| One accent wall | 12 × 8 ft (96 ft²) | 1 gal |
Figures use this calculator's default settings; tap one above the inputs to load it and adjust.
The formula
Gallons = (Wall area × Coats) ÷ 350 ft² per gallon
Example: 400 ft² of wall × 2 coats = 800 ÷ 350 = 2.3 → 3 gallons.
How it works
- 1Multiply wall area by the number of coats for total coverage.
- 2Divide by 350 ft² (the coverage of one gallon) and round up.
- 3Buy a little extra for touch-ups — paint batches are hard to match later.
Frequently asked questions
Does one gallon really cover 350 square feet?
That's the typical figure for smooth, primed walls. Rough or porous surfaces and dark-to-light color changes reduce coverage, so round up.
How much paint do I need for a 12 × 12 room?
A 12 ft × 12 ft room with 8 ft ceilings has 384 ft² of wall before subtracting doors and windows. Two coats is 768 ft², and 768 ÷ 350 = 2.2, so buy 3 gallons. The ceiling adds 144 ft², which is about 1 gallon for two coats.
How do I work out my wall area?
Add the lengths of all the walls to get the room's perimeter, then multiply by the ceiling height. Subtract about 20 ft² for each standard door and 15 ft² for each average window if you want a tighter number.
How many coats of paint do I need?
Plan on two coats for an even finish. One coat can be enough when you are repainting the same colour with a quality paint. New drywall and big colour changes need a primer coat first.