Coverage by surface type, room size table, formula, and shopping list for interior paint.
Quick answer
One gallon of paint usually covers 350–400 sq ft
for one coat on smooth, primed walls. For two coats, one gallon covers about
175–200 sq ft. A 12×12 room with 9 ft ceilings
usually needs about 2 gallons for two coats.
- 1 gallon covers 350–400 sq ft for one coat on smooth walls
- For two coats, 1 gallon covers about 175–200 sq ft
- A 12×12 room usually needs about 2 gallons for two coats
- Textured walls may cover only 250–350 sq ft per gallon
- Buy one extra quart as a small buffer if you are close to the limit
Paint Coverage Per Gallon by Surface Type
| Surface Type | Coverage Per Gallon | Notes |
|---|---|---|
| Smooth, primed wall | 350–400 sq ft | Standard interior latex, one coat |
| Lightly textured wall | 300–350 sq ft | Older plaster or light orange-peel texture |
| Heavy texture or bare drywall | 250–300 sq ft | Prime first because bare drywall absorbs paint |
| Ceiling paint | 350–400 sq ft | Similar to walls on smooth, primed ceilings |
| Exterior surfaces | 250–350 sq ft | Rough siding, masonry, and porous surfaces use more paint |
The Formula
Gallons needed = paintable square feet × coats ÷ coverage per gallon
Paintable square feet means total wall area minus doors and windows.
A standard interior door usually removes about 21 sq ft, and a standard
window removes about 15 sq ft.
Example: 12×12 room, 9 ft ceiling, 2 coats
- Wall area = 2 × (12 + 12) × 9 = 432 sq ft
- Subtract 1 door and 2 windows: 432 – 51 = 381 sq ft
- 381 × 2 coats ÷ 400 coverage = 1.9
- Round up: 2 gallons
For your exact room size, use the
Paint Calculator.
It can include ceilings, primer, trim, doors, windows, and multiple rooms.
Gallons Needed by Room Size
These examples assume 9 ft ceilings, one door, two windows, and 400 sq ft
of coverage per gallon.
| Room Size | Paintable Sq Ft | 1 Coat | 2 Coats |
|---|---|---|---|
| 10×10 | ~309 sq ft | 1 gallon | 2 gallons |
| 12×12 | ~381 sq ft | 1 gallon | 2 gallons |
| 14×16 | ~489 sq ft | 2 gallons | 3 gallons |
| 20×20 | ~669 sq ft | 2 gallons | 4 gallons |
Does Ceiling Paint Cover the Same Area?
Yes. Ceiling paint usually covers about 350–400 sq ft per gallon on a smooth,
primed ceiling. A 12×12 ceiling is 144 sq ft, so one gallon can usually cover
two coats. A 20×20 ceiling is 400 sq ft, so plan on about one gallon per coat.
Frequently Asked Questions
How many square feet does one gallon of paint cover?
One gallon covers about 350–400 sq ft for one coat on smooth, primed walls.
Textured or unprimed surfaces may cover only 250–300 sq ft.
Is one gallon enough to paint a 12×12 room?
One gallon is usually enough for one coat. For two coats, a 12×12 room
usually needs about 2 gallons.
How much does one gallon cover with two coats?
With two coats, one gallon effectively covers about 175–200 sq ft.
Does ceiling paint coverage differ?
Ceiling paint coverage is usually similar to wall paint on smooth, primed
surfaces: about 350–400 sq ft per gallon.
Do textured walls use more paint?
Yes. Texture reduces coverage because the surface absorbs more paint.
Plan for 250–350 sq ft per gallon depending on how rough the wall is.
Related Calculators
- Paint Calculator — exact gallons for any room
- Flooring Calculator — square footage for flooring projects
- Tile Calculator — tile count, boxes, and waste