How Much Paint for a 12x12 Garage? (2026 Guide)
A 12x12 ft single-car garage with 9-ft walls and a 9x7 garage door has about 360 sq ft of net wall after openings — two coats of finish take about 3 gallons; paint the ceiling too and add about 1 gallon.
Paint for a 12x12 garage at a glance
We'll assume a 12×12 ft single-car garage (144 sq ft floor) with 9-ft walls, one 9×7 garage door (63 sq ft), a small side door or window (about 12 sq ft), and the standard baseline of 1 gallon ≈ 350 sq ft per coat on smooth, primed drywall. Two finish coats double the area, so every row is (net area × 2) ÷ 350, rounded up to the whole gallon.
| Job scope | Net area per coat | Two coats need | Paint to buy |
|---|---|---|---|
| Walls only | 357 sq ft | 714 sq ft | 3 gallons (2.04 rounds up) |
| Walls + ceiling | 501 sq ft | 1,002 sq ft | 3 gallons (2.86 rounds up) |
| Ceiling only, as an add-on | 144 sq ft | 288 sq ft | 1 gallon (0.82 rounds up) |
Adding the ceiling keeps the finish order at three gallons — 1,002 sq ft of coverage against three cans' 1,050 leaves a thin margin, so budget a fourth gallon for cut-in. On bare drywall, add 1 gallon of primer for the walls first.
A full working example
Here's the full calculation for a 12×12 garage with 9-ft walls and a 9×7 door.
1. Find the net wall area
Walls form a rectangle: perimeter × height. The perimeter of a 12×12 garage is 48 ft, so gross wall area = 48 × 9 = 432 sq ft. Subtract what you won't paint: the 9×7 garage door = 63 sq ft plus about 12 sq ft of side door and window. Net wall area = 432 − 75 = 357 sq ft.
2. Double it for two coats
Every coat covers the full wall area, so two coats need 357 × 2 = 714 sq ft of paint coverage.
3. Divide by coverage and round up
714 ÷ 350 ≈ 2.04 gallons. Paint comes in whole gallons and 2 gallons covers only 700 sq ft — just short — so buy 3 gallons, with surplus for touch-ups. If you also paint the 144-sq-ft ceiling, its two coats add 288 sq ft (≈0.8 gallon), which rounds to 1 gallon.
Other garage sizes, same math
The 350-sq-ft-per-gallon baseline and the subtract-the-openings step repeat across garage sizes — our square-feet-per-gallon guide explains how coverage changes on rough or unprimed walls. A two-car 16×20 garage nets about 523 sq ft and still lands near 3 gallons (1,046 ÷ 350 ≈ 3.0), while a wide 20×20 nets about 588 sq ft and runs closer to 4 (our 2-car garage guide walks through it). A door smaller than 9×7 leaves more wall, but the total moves by less than a gallon.
Garage painting tips
- Deduct the garage door, then measure the rest — the 9×7 door (63 sq ft) is what keeps this estimate low; an 8×7 door (56 sq ft) leaves about 364 sq ft net (728 ÷ 350 ≈ 2.08), still a three-gallon order. Subtract every opening before dividing, or you'll overbuy by a full gallon.
- Prime bare drywall first — the 350-sq-ft-per-gallon figure assumes a smooth, primed surface. Unpainted gypsum soaks up finish unevenly, so seal the 357 sq ft of walls with one coat of drywall primer (about 400 sq ft per gallon, so one can does it) before your two finish coats.
- The floor is a separate job — wall paint isn't made for foot traffic, vehicles or moisture. Coat the slab with epoxy or concrete floor paint instead — and price it separately, since it covers a different area per gallon.
Measure once, then let the tool finish the division: Calculate your exact paint amount →
FAQ
How many gallons of paint do the walls of a 12x12 garage need?
About 3 gallons of finish paint. The walls net about 357 sq ft after the 9×7 garage door (63 sq ft) and a small side opening: 48 × 9 = 432 sq ft gross, minus 75 sq ft of openings. Two coats need 714 sq ft, and 714 ÷ 350 ≈ 2.04, so you buy 3 gallons.
Is a single-car garage much cheaper to paint than a two-car garage?
Not as much as you'd expect. A 12×12 single-car garage nets about 357 sq ft of wall (3 gallons of finish over two coats), and a two-car 16×20 layout nets about 523 sq ft and still lands near 3 gallons (1,046 ÷ 350 ≈ 3.0). Door count and wall height move the total more than the floor plan: a wide 20×20 two-car garage nets about 588 sq ft and runs closer to 4 gallons, as our 2-car garage paint guide shows.
Should I paint the ceiling of a 12x12 garage?
You can skip it. The 144-sq-ft ceiling is the one surface most garages leave bare, and dropping it trims the job by about a gallon: two coats need 288 sq ft ÷ 350 ≈ 0.8 gallon. If you do paint it, budget about 1 more gallon, and prime bare drywall before the finish coats.
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