Paint Calculator
Estimate from your measurements. The coverage on your can takes priority, and textured or porous walls can use more.
To estimate paint, multiply the wall area by the coats and divide by the coverage. A 12 × 10 ft room with 8 ft walls has 316 ft² after a door and a window. Two coats at 350 ft² per gallon take 1.81 gallons, or about 2 with a 10% reserve. Enter your room below to get gallons and the cans to buy.
How far does a can of paint go?
| Can | 1 coat at 250 ft²/gal | 1 coat at 350 ft²/gal | 1 coat at 400 ft²/gal | 2 coats at 350 ft²/gal |
|---|---|---|---|---|
| 1 quart | 63 ft² | 88 ft² | 100 ft² | 44 ft² |
| 1 gal | 250 ft² | 350 ft² | 400 ft² | 175 ft² |
| 2 gal | 500 ft² | 700 ft² | 800 ft² | 350 ft² |
| 5 gal | 1,250 ft² | 1,750 ft² | 2,000 ft² | 875 ft² |
How to calculate how much paint you need
There are three steps:
- Area: room perimeter × wall height, minus doors and windows, plus the ceiling if you're painting it.
- Gallons: area × coats ÷ coverage per gallon.
- Reserve: add 10 to 15% from the same batch for touch-ups.
A 12 × 10 ft room has a 44 ft perimeter. With 8 ft walls, that's 352 ft². Take off 21 ft² for a 3 × 7 ft door and 15 ft² for a 3 × 5 ft window, and 316 ft² remain. Two coats make 632 ft², and 632 ÷ 350 = 1.81 gallons. With a 10% reserve, that's 1.99 gallons, so 2 gallons is right.
How much does a gallon cover?
Sherwin-Williams says a gallon typically covers about 350 to 400 ft², and that texture and the coverage you want may mean buying a little extra. This calculator starts at 350 to stay on the cautious side, with a 250 ft² preset for textured walls. That 250 is a planning figure rather than a published one. Check the can, and see the table above for how far each size goes.
Common rooms
With 8 ft walls, a door, a window, two coats, 350 ft² per gallon, and a 10% reserve, a 10 × 10 ft room takes about 1.8 gallons, a 12 × 12 ft room about 2.2, and a 20 × 15 ft room about 3.3. Adding the ceiling to the 12 × 12 ft room brings it to about 3 gallons.
Coats, primer, and surfaces
- Light repaint: Over a light, already painted wall, a high-hiding paint may need just one coat. Two is the standard.
- Strong colors and blotchy walls: These often need three coats. Change the Coats field to match.
- Primer: A gallon covers roughly 200 to 300 ft². Run the calculator again with one coat and 250 ft² per gallon.
- Texture: Paint use depends on wall texture and absorbency. Start low on coverage and paint a test patch if the wall is rough or bare.
- Ceilings: Ceiling paint can have a different coverage. Choose Yes for the ceiling if one paint covers everything, or use Known area to estimate it separately.
What the calculator leaves out
Doors and windows use fixed sizes. For a wall of windows or a sliding door, work out the wall area with the square footage calculator and enter it under Known area. Window reveals and the wall behind radiators are usually brushed and take more paint. Trim, doors, and exterior walls need their own paint and coverage figure, so run them separately. If a wall is getting paper, use the wallpaper calculator instead.
Buying the paint
The calculator finds the smallest total from 5 gallon pails, gallons, and quarts that covers your need. That isn't always the cheapest choice, because small cans usually cost more by volume, so compare the price per gallon. If a larger can costs nearly the same, take it and keep the rest for touch-ups. Enter a price per gallon above and the cost is based on what you buy, not just what you use.
Common mistakes
- Using floor area. A 120 ft² room has 352 ft² of wall at 8 ft high.
- Forgetting the second coat. It doubles the paint, and it is the most common reason to run short.
- Planning on the best coverage. The top of the range assumes a smooth, well-prepared wall. Rough or bare walls use more.
- Buying tinted paint too tight. A second batch can look slightly different, so buy a little more, especially when the color is mixed for you.
Coverage comes from Sherwin-Williams, the door and window sizes are simple rounded dimensions, and the examples and table are checked against this calculator. Your paint's label always takes priority.
Frequently asked questions
How much paint do I need for a room?
Multiply the wall area by the coats and divide by the coverage. A 12 × 10 ft room with 8 ft walls has 316 ft² after a door and a window. Two coats at 350 ft² per gallon take 1.81 gallons, or about 2 gallons with a 10% reserve.
How many square feet does a gallon of paint cover?
About 350 to 400 ft² in one coat on a smooth wall, according to Sherwin-Williams. Textured or porous walls take more paint, so plan on less coverage there. The can gives the figure for your product.
How much paint do I need for a 12 × 12 room?
About 2.25 gallons with 8 ft walls: 2 gallons and a quart. That is 348 ft² after a door and a window, two coats at 350 ft² per gallon, and a 10% reserve. Add the ceiling and it goes up to about 3 gallons.
How much paint do I need for 1,000 square feet?
For 1,000 ft² of wall, two coats at 350 ft² per gallon take about 5.7 gallons, or 6.3 with a 10% reserve. If 1,000 ft² is the floor area of your home, the wall area is much larger, so measure room by room.
How many coats of paint do I need?
Usually two. One can be enough when you repaint a light wall in a similar color with a high-hiding paint. Strong colors and blotchy walls often need three.
Should I subtract doors and windows?
For a big job, yes. The calculator takes off 21 ft² per door (3 × 7 ft) and 15 ft² per window (3 × 5 ft). Set the counts to zero for a more generous estimate, or use the area option for your own number.
How do I calculate wall square footage?
Multiply the room perimeter by the wall height, then subtract doors and windows. A 12 × 10 ft room has a 44 ft perimeter, so 8 ft walls come to 352 ft². For one wall, multiply its width by its height.
How much primer do I need?
A gallon of primer covers roughly 200 to 300 ft², according to Sherwin-Williams. Run the calculator separately with one coat and 250 ft² per gallon to get a primer estimate.
Does the ceiling need different paint?
Often, yes. Ceiling paint can have a different coverage, so the calculator shows the ceiling area for you to price separately if needed. It uses one coverage figure for walls and ceiling together.
Should I buy a gallon or quarts?
Compare the price per gallon, since quarts usually cost more by volume. The calculator shows the smallest total that covers your need, which can include quarts. If one extra gallon is close in price, it may be the better buy.
Related calculators
Sources
- Paint CalculatorSherwin-WilliamsA gallon typically covers about 350 to 400 ft²; a gallon of primer roughly 200 to 300 ft².
- Wandfarbe-Rechner (in German)deutschland-rechner.deTwo coats as the standard, three for strong colors or blotchy walls, and a 10 to 15% reserve from the same batch.
- Farbmenge berechnen (in German)sanier.deWall and ceiling area, the effect of texture and absorbency, and comparing price by volume.