How far a gallon goes
Most interior wall paints cover about 350–400 square feet per gallon per coat on smooth, primed walls. The can lists the exact figure for that product. Using 350 sq ft gives you a little margin.
| Container | Typical coverage per coat |
|---|---|
| Quart | about 90–100 sq ft |
| Gallon | about 350–400 sq ft |
| 5-gallon bucket | about 1,750–2,000 sq ft |
Rough, textured or very porous surfaces such as new drywall, stucco and bare wood soak up more paint, often 10–25% more.
The method
- Wall area: add the lengths of all the walls (the perimeter) and multiply by the ceiling height.
- Subtract openings: about 20 sq ft for each standard door and 15 sq ft for each average window.
- Multiply by the number of coats. Two coats is standard for a color change or fresh walls.
- Divide by the coverage (350 sq ft per gallon) and round up.
Example: a 12 × 14 ft bedroom
With 8 ft ceilings, the walls are 2 × (12 + 14) × 8 = 416 sq ft. Take off one door (20 sq ft) and two windows (30 sq ft) and you have 366 sq ft to paint.
Two coats is 732 sq ft. At 350 sq ft per gallon that's about 2.1 gallons, so buy 2 gallons plus a quart, or 3 gallons if you want spare for touch-ups. The ceiling is 12 × 14 = 168 sq ft, so two coats need about 1 gallon of ceiling paint.
The paint calculator does this from your room size, openings and number of coats.
Gallons by room size
Walls only, 8 ft ceilings, one door and two windows, two coats at 350 sq ft per gallon:
| Room | Paintable wall area | Gallons (2 coats) |
|---|---|---|
| Small bathroom, 5 × 8 ft | about 160 sq ft | about 1 |
| Bedroom, 10 × 12 ft | about 300 sq ft | about 2 |
| Bedroom, 12 × 14 ft | about 365 sq ft | 2–2½ |
| Living room, 15 × 20 ft | about 510 sq ft | about 3 |
| Large room, 20 × 24 ft | about 650 sq ft | about 4 |
Taller ceilings, extra doors or windows, and open-plan spaces change the numbers quickly, so measure your own room.
How many coats?
- Same or similar color, walls in good shape: one coat may do, but two gives a more even finish.
- Color change: two coats. Going from a dark color to a light one may need a primer first, or a third coat.
- New drywall: one coat of drywall primer, then two finish coats. Primer usually covers less, often around 200–300 sq ft per gallon on bare drywall.
- Paint-and-primer products help over previously painted walls but don't replace a dedicated primer on bare drywall, stains or glossy surfaces.
Ceilings, trim and doors
Ceilings use flat ceiling paint and are measured as length × width. For trim, a quart is usually enough for the baseboards and casings of an average room. A standard interior door needs roughly a quart for two coats on both sides. If you're painting all the trim in a house, buy by the gallon.
Buying tips
- Buy everything for the job at once, or ask the store to box (mix) the gallons together. Tinted batches can vary slightly.
- Keep a little leftover paint, labeled with the room and color code, for touch-ups.
- Two gallons plus a quart is often cheaper than three gallons, so check prices.
- If the house was built before 1978, test old paint for lead before sanding or scraping.
Planning new walls too? The drywall calculator works out sheets, mud and tape from the same room measurements.