How much paint a room takes, ceiling included
The four walls less the doors and windows, plus the ceiling, times two coats, over 350 square feet a gallon. A 12 by 12 foot room with 8 foot walls, one door and one window, is 349 square feet of wall and 144 of ceiling: 493 square feet, twice over, is 2.82 gallons. Buy three 1-gallon cans and paint the walls and the ceiling from the same ones.
That is the room Inch Calculator answers with "most likely 2 gallons". Its 2 gallons are one coat: 528 square feet of walls and ceiling over 350 is 1.51. Paint the second coat most rooms need, take out a 20 square foot door and a 12 square foot window as Inch does, and it is (528 − 32) × 2 = 992 square feet, 2.83 gallons — three cans, not two.
Rooms by size
Behr's calculator offers small, medium and large rooms without saying how big they are. Here are four, with the measurements written out, each with one door, two coats on the walls and the ceiling, 8 foot walls:
| Room | Walls and ceiling | Two coats buys |
|---|---|---|
| 10 × 10 ft, 1 window | 385 ft² | 2 gal + 1 qt |
| 12 × 12 ft, 1 window | 493 ft² | 3 gal |
| 12 × 14 ft, 2 windows | 534 ft² | 3 gal + 1 qt |
| 14 × 16 ft, 2 windows | 654 ft² | 4 gal |
Those are at 350 square feet a gallon with the page's estimated prices; at 400, the top of Sherwin-Williams' range, every one of them takes about an eighth less. Type your own room above for your own answer.
Several rooms in one job
Add a room for each room, and the page adds them up before it buys: two 12 by 12 rooms are 986 square feet, and two coats of that is 5.63 gallons, cheapest as a 5-gallon pail and one gallon can rather than six gallon cans. A hallway is a room too — its length, its width and its wall height — and a single wall is a rectangle, its width by its height. Taking the cans for the whole job at once is how the 5-gallon pail comes into it; room by room, it never does.
When the ceiling is a different paint
Ceiling paint is often a flat white that the walls are not. Then this is two purchases: choose "Walls" under "What to paint" for the wall color, then "Ceiling" for the ceiling on its own. A 12 by 12 ceiling, two coats, is 0.82 gallons: one gallon can.
Paint prices on this page are our own estimates, not a store's: type yours beside each can. We are not connected with any brand or store named here.