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.
Coverage per gallon, by paint
One coat, as each maker prints it on its data sheet or product page. Rough or porous walls take more paint than smooth, primed ones, so plan on the low end of a range; Glidden gives one figure, for primed, smooth walls. The last column is this guide’s room: 314 sq ft of wall, two coats, at the low end.
| Paint | Maker | Covers a gallon, one coat | This room, two coats |
|---|---|---|---|
| Emerald Interior (matte) | Sherwin-Williams | 350 to 400 sq ft | 1.8 gal: buy 2 gallons |
| SuperPaint Interior (satin) | Sherwin-Williams | 350 to 400 sq ft | 1.8 gal: buy 2 gallons |
| Duration Home Interior (flat) | Sherwin-Williams | 350 to 400 sq ft | 1.8 gal: buy 2 gallons |
| Regal Select (semi-gloss) | Benjamin Moore | 400 to 450 sq ft | 1.6 gal: buy 2 gallons |
| Ben (semi-gloss) | Benjamin Moore | 400 to 450 sq ft | 1.6 gal: buy 2 gallons |
| Aura (eggshell) | Benjamin Moore | 350 to 400 sq ft | 1.8 gal: buy 2 gallons |
| Premium Plus Interior | Behr | 250 to 400 sq ft | 2.5 gal: buy 3 gallons |
| Signature Interior | Valspar | 200 to 400 sq ft | 3.1 gal: buy 3 gallons and a quart |
| Ultra Interior | Valspar | 300 to 400 sq ft | 2.1 gal: buy 2 gallons and a quart |
| Diamond Interior (semi-gloss) | Glidden | About 400 sq ft on primed, smooth walls | 1.6 gal: buy 2 gallons |
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.