Measure the room or the wall, count the doors and windows. You get how much paint to buy, in the cans it is sold in.
Paint to buy
2 gallonsfor 2 coats on 334 sq ft of wall
Quick answer: one gallon of paint covers about 350–400 sq ft of smooth wall per coat, and most walls need two coats. To find how much paint you need, multiply the room’s perimeter by the wall height. Take off about 20 sq ft for each door and 15 for each window, double it for two coats, and divide by 350. A 12 × 12 ft room with 8 ft walls takes 2 gallons. The calculator above does it for your room, in the gallons and quarts paint is sold in.
How to use the paint calculator
- Choose a whole room or one wall. For a room, enter the floor’s length and width; for an accent wall, its width.
- Enter the wall height from the floor to the ceiling, and count the doors and windows.
- Pick the coats and the surface. Two coats is the usual; textured, rough or porous walls take more paint.
- Add the ceiling or primer if you need them. They are listed separately, because they are different cans.
- Read what to buy: gallons and quarts, the exact amount, and the square footage behind it. Copy link takes the list to the store.
The rules the calculator uses
How many square feet a gallon of paint covers
Most interior paint cans say 350–400 sq ft per gallon, per coat, on a smooth, primed wall. The calculator uses 350, the low end, because rollers, edges and touch-ups always use a little more than the label. Textured, rough or porous walls, like fresh plaster or unprimed drywall, drink more: about 250–300 sq ft per gallon, so the calculator uses 275. A quart is a quarter of a gallon and covers about 90 sq ft.
How to work out the wall area
For a room, add the four wall lengths (the perimeter) and multiply by the wall height. A 12 × 12 ft room with 8 ft walls has 48 × 8 = 384 sq ft of wall. Take off what you are not painting: about 20 sq ft for a door and 15 sq ft for a window. One door and two windows leave 334 sq ft.
How many coats of paint
Two coats is the rule for an even finish. One coat is enough only when you repaint in the same color over paint in good condition. Three coats may be needed for a big change, like white over deep red. A coat of primer and then two coats of paint often does that job better and costs less.
How much primer
Primer goes on in one coat and covers a little less than paint: about 300 sq ft per gallon on smooth walls and 250 on textured ones. Use it on new drywall, bare wood, patched areas, stains, and when going from a dark color to a light one.
How paint is sold, and how the calculator rounds
Paint comes in quarts, gallons and 5-gallon buckets. Two quarts usually cost about as much as a gallon, so the calculator adds at most one quart, and rounds anything more up to a gallon. Within a tenth of a gallon of a whole can, the cans you already have will cover it. Buying all the paint for a room at once also keeps the color identical from can to can.
How much paint for a room: chart
8 ft walls, one door, two windows, two coats, smooth walls:
| Room | Wall area to paint | Wall paint | Ceiling paint |
|---|---|---|---|
| 10 × 10 ft | 270 sq ft | 2 gallons | 1 gallon |
| 10 × 12 ft | 302 sq ft | 2 gallons | 1 gallon |
| 12 × 12 ft | 334 sq ft | 2 gallons | 1 gallon |
| 12 × 14 ft | 366 sq ft | 2 gallons | 1 gallon |
| 14 × 16 ft | 430 sq ft | 3 gallons | 2 gallons |
| 16 × 20 ft | 526 sq ft | 3 gallons | 2 gallons |
| 20 × 20 ft | 590 sq ft | 4 gallons | 3 gallons |
Paint coverage per can
| Can | Smooth wall, one coat | Textured wall, one coat |
|---|---|---|
| Quart | about 90 sq ft | about 70 sq ft |
| Gallon | 350–400 sq ft | 250–300 sq ft |
| 5-gallon bucket | 1,750–2,000 sq ft | 1,250–1,500 sq ft |
Three worked examples
A 12 × 14 ft bedroom with primer. With 8 ft walls, one door and two windows, there are 366 sq ft to paint. Two coats need 2.09 gallons, which is 2 gallons: 350 sq ft is the low end of what a gallon covers, so the last tenth is covered. Priming the walls first takes 1 gallon and 1 quart of primer.
An accent wall, 12 ft wide and 8 ft high. That is 96 sq ft, and two coats need just over half a gallon. Two quarts would cost about as much as a gallon, so buy 1 gallon. The rest is useful for touch-ups.
A 16 × 20 ft living room with 9 ft ceilings. With two doors and three windows, there are 563 sq ft to paint. Two coats need 3.22 gallons: 3 gallons and 1 quart.
Common paint-buying mistakes
- Measuring the floor instead of the walls. A 12 × 12 room has 144 sq ft of floor but 384 sq ft of wall at 8 ft high.
- Planning one coat. A single coat almost always shows roller marks and patches. Plan for two.
- Buying one can at a time. Tints can vary slightly between batches. Buy the room’s paint together, and mix the cans in a bucket if you have more than one.
- Using wall paint on the ceiling. Ceiling paint is flatter and spatters less. It is its own line on the list.
- Skipping primer on new drywall. Bare drywall soaks up the first coat unevenly. One coat of primer saves paint.
Read next
- Can you use the same paint for walls and ceilings?
- Flat or satin paint for the ceiling
- Paint colors for small rooms
- Living room paint color ideas
- A geometric accent wall painting tutorial
Paint questions
How many square feet does a gallon of paint cover?
About 350–400 sq ft per coat on a smooth, primed wall, and about 250–300 sq ft on a textured or porous one. For two coats, halve it: a gallon paints roughly 175–200 sq ft of wall twice.
How much paint do I need for a 12×12 room?
2 gallons for two coats on 8 ft walls, with one door and two windows: 334 sq ft of wall. Add 1 gallon of ceiling paint if you are painting the ceiling too.
How much paint for a bedroom?
Most bedrooms, from 10 × 10 ft to 12 × 14 ft with 8 ft walls, take 2 gallons for two coats. A larger bedroom, 14 × 16 ft, takes 3 gallons.
How much does a quart of paint cover?
About 90 sq ft of smooth wall in one coat, a quarter of what a gallon covers. That is enough to paint a small wall, a door or a piece of furniture, but not an accent wall in two coats.
How many coats of paint do I need?
Two for an even finish. One is enough only when you repaint the same color over sound paint. A big color change can need three, or one coat of primer and two coats of paint.
How many coats of primer do I need?
One coat on most surfaces. Two can help on raw wood, heavy stains, or when covering a very dark color with a light one.
How much paint for an accent wall?
A typical accent wall, 12 × 8 ft, is 96 sq ft. Two coats need just over half a gallon, so buy 1 gallon: it costs about the same as two quarts and leaves some for touch-ups.
Choosing colors for the whole room? Try your layout and furniture in the free 2D planner before you paint.
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