How Much Paint Do I Need for a Room?
A room-by-room chart of net wall area, gallons and cans for twelve common sizes, plus the arithmetic to do it yourself for any room.
Most single rooms take 2 to 3 gallons of wall paint for two coats. A 12x12 room with 8 ft ceilings, one door and one window has 348 sq ft of net wall and needs 1.99 gallons; with 10% waste that is 2 gallons plus a quart. For a size that is not listed, do this: multiply the room's perimeter by the ceiling height, subtract 21 sq ft per door and 15 sq ft per window, multiply by the number of coats, then divide by 350 sq ft per gallon.
Rates and coverage figures updated August 2026.The table below covers the twelve room sizes people ask about most. Each row lists the net wall area, the gallons two coats require, and the smallest set of cans that covers it once 10% waste is added. Every row rests on one basis: 8 ft ceilings, one door at 21 sq ft, one window at 15 sq ft, two coats, and 350 sq ft per gallon on smooth primed drywall. Change any of those and the answer moves, so read the basis before you read the row. The coverage chart holds the constants behind it.
One thing this chart makes visible that almost nobody states out loud: wall paint follows the room's perimeter, not its floor area. Walk the walls, not the carpet. That is why 12x12 and 10x14 are twins here, 48 ft around, 348 sq ft of net wall, 1.99 gallons each, even though one holds 144 sq ft of floor and the other 140. The same pairing repeats three more times: 10x12 with 11x11 at 44 ft, 12x14 with 13x13 at 52 ft, 14x14 with 12x16 at 56 ft. A square room and a long narrow one can want identical cans. Only 10x10, 12x13, 12x15 and 15x15 stand alone in this set.
The corollary is worth keeping when somebody hands you a shortcut. Wall area divided by floor area runs from 2.84 on a 10x10 down to 1.97 on a 15x15, because a small room carries far more perimeter per square foot of floor. A flat "walls are 2.5 times the floor" rule therefore underbuys small rooms and overbuys large ones, in opposite directions. Measure around.
| Room | Floor (sq ft) | Perimeter | Net wall (sq ft) | Gallons, 2 coats | Buy | Paint cost | Pro, walls |
|---|---|---|---|---|---|---|---|
| 10x10 ft | 100 | 40 ft | 284 | 1.62 | 2 × 1-gallon cans | $80 | $396 |
| 10x12 ft | 120 | 44 ft | 316 | 1.81 | 2 × 1-gallon cans | $80 | $441 |
| 11x11 ft | 121 | 44 ft | 316 | 1.81 | 2 × 1-gallon cans | $80 | $441 |
| 10x14 ft | 140 | 48 ft | 348 | 1.99 | 2 × 1-gallon cans + 1 × quart | $96 | $486 |
| 12x12 ft | 144 | 48 ft | 348 | 1.99 | 2 × 1-gallon cans + 1 × quart | $96 | $486 |
| 12x13 ft | 156 | 50 ft | 364 | 2.08 | 2 × 1-gallon cans + 2 × quarts | $112 | $508 |
| 12x14 ft | 168 | 52 ft | 380 | 2.17 | 2 × 1-gallon cans + 2 × quarts | $112 | $530 |
| 13x13 ft | 169 | 52 ft | 380 | 2.17 | 2 × 1-gallon cans + 2 × quarts | $112 | $530 |
| 12x15 ft | 180 | 54 ft | 396 | 2.26 | 2 × 1-gallon cans + 2 × quarts | $112 | $553 |
| 12x16 ft | 192 | 56 ft | 412 | 2.35 | 3 × 1-gallon cans | $120 | $575 |
| 14x14 ft | 196 | 56 ft | 412 | 2.35 | 3 × 1-gallon cans | $120 | $575 |
| 15x15 ft | 225 | 60 ft | 444 | 2.54 | 3 × 1-gallon cans | $120 | $620 |
How to work it out for any room
Here is the full calculation behind the 12x12 row. Run the same six steps on a room that is not in the chart and you get its number too.
- Perimeter: (12 + 12) x 2 = 48 ft around the room.
- Gross wall: 48 ft x 8 ft ceiling = 384 sq ft.
- Openings: subtract 21 sq ft for the door and 15 sq ft for the window, leaving 348 sq ft of net wall.
- Coats: 348 x 2 = 696 sq ft of coverage to buy.
- Gallons: 696 ÷ 350 = 1.99 gallons.
- Waste: 1.99 x 1.10 = 2.19 gallons, bought as 2 gallons plus 1 quart.
Now test what actually breaks that number. Openings subtract, so a second window drops the 12x12 to 1.90 gallons and a second door to 1.87, while a room with no window at all climbs to 2.07. Height does far more work: a 9 ft ceiling takes the same room to 2.26 gallons and a 10 ft ceiling to 2.54. So does texture, since it swallows paint. Orange peel puts you at 2.14 and knockdown at 2.53, which is a third can on a room the chart calls two. Bare drywall, stains, or a drastic color change add primer, and a drastic change may want three coats instead of two.
Buying is the last step. A quart runs about 40% of a gallon's price, so topping off with quarts beats rounding up whenever you are barely over a line. A 5-gallon pail at $150 only pays off past roughly 4.3 gallons, which no single room here reaches. To sketch an odd-shaped room instead of doing the arithmetic, use the room planner or the quick gallons estimator.
If your room is not on the chart, open the nearest size and change the dimensions — each page carries a calculator that recomputes everything, including what to buy. For several rooms at once use the paint estimator, and to work from a real floor plan with its actual doors and windows use the visual paint planner.
Paint by the room, answered
How much paint do I need for a 12x12 room?
348 sq ft of net wall, which is 1.99 gallons for two coats. Add 10% for waste and roller loss and you buy 2 gallons plus 1 quart, about $96 in materials at $40 per gallon. Basis: 8 ft ceilings, one door, one window, 350 sq ft per gallon.
How many gallons of paint does a bedroom take?
Two to three gallons covers nearly every bedroom on this chart at two coats. A 10x10 needs 1.62 gallons and buys as 2 gallons. A 15x15 needs 2.54 and buys as 3. Ceilings above 8 ft push you up a can, so measure your height before you buy.
Does an extra window mean I need more paint?
No. A window is a hole in the wall, so it removes paintable surface. On the 12x12 row, a second window takes the requirement from 1.99 gallons down to 1.90, and a second door takes it to 1.87. Deleting the window is what raises it, to 2.07 gallons.
Why do two rooms with different floor areas need the same paint?
Because walls are priced by perimeter, not floor. A 12x12 and a 10x14 both measure 48 ft around, so both have 348 sq ft of net wall and both need 1.99 gallons, despite 144 versus 140 sq ft of floor. Shape changes the floor number without changing the walls.
Do these numbers include the ceiling and trim?
No. Every row is walls only. Ceiling paint covers about 350 sq ft per gallon on a flat ceiling and about 225 on popcorn texture, so a 12x12 ceiling takes roughly a half gallon per coat. Trim covers about 250 sq ft per gallon and is usually a separate quart or gallon.
What would a painter charge to do the same room?
Interior repaint runs $1.00 to $3.00 per sq ft of paintable wall, around $1.75 in the middle. That puts a 12x12 near $486 and a 15x15 near $620. Watch for a $250 to $500 job minimum, which a single small room can fall under, making one room cost the same as two.