How much paint do I need? Coverage, coats and primer
Measure the walls (perimeter times height), take out doors and windows, multiply by the number of coats and divide by the coverage on the can, often about 400 sq ft per gallon. Most rooms need two coats.
A 12 × 10 ft room with 8 ft walls has 352 sq ft of wall. Less one door and two windows that is 314 sq ft, so two coats take 1.57 gallons: buy 2, plus 1 of primer.
Worked example
Example: a 12 × 10 ft room with 8 ft walls, one door and two windows (38 sq ft), two coats and 400 sq ft per gallon.
This example gives 2 1-gallon paint cans.
- Surface area: 314 sq ft
- ceil(314 × 2 × (1 + 0/100) ÷ 400) = 2
Other calculators for this job
Every step of a paint and drywall project: measure, the list, what it costs and the quotes.
What changes the order?
Each coat covers the same walls again. Cans round up, so a small extra surface may fit in the cans already counted.
| Calculator input | Result from those inputs |
|---|---|
| Paint coats: 1 | 1 can (1 gallon) |
| Paint coats: 2 | 2 cans (1 gallon) |
| Paint coats: 3 | 3 cans (1 gallon) |
Try your own measurements in the paint calculator.
Measure what gets paint
Walls are the room’s perimeter times its height. Take out each door (about 17 sq ft for a 30 × 80 inch door) and window (about 11 sq ft for a 32 × 48 inch one). The ceiling is its length times its width. Trim, doors and cabinets are separate, often in a different finish.
Coats and primer
Two coats cover most colors evenly. Prime new drywall, bare patches and big changes of color; primer has its own coverage on its can.
Coverage on the can
Read the coverage on the paint you chose. Sherwin-Williams calls its 400 sq ft per gallon a theoretical figure: rough or porous walls take more. If the label gives a range, plan on the low end.
Buy by the room and color
Rooms in the same color and finish share cans; each color is its own order. A quart covers about 100 sq ft at 400 sq ft per gallon, enough for an accent wall or trim.