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Paint Calculator
Enter a room’s length, width and wall height to find how many gallons of paint to buy. The calculator subtracts doors and windows, multiplies by the number of coats, and lets you set the coverage printed on your can.
- Gallon cans to buy
- 3
- Area to paint (one coat)
- 365 ft²
- Paint cost
- $105.00
Saved setups
Save a set of inputs you reuse — your usual rate, your loan, your room sizes — and load it back in one tap.
Your recent calculations
Results you calculate here are kept on this device so you can come back to them.
Formula
How to use it
- Enter the room’s length, width and wall height.
- Enter how many doors and windows to leave out.
- Tick the ceiling if you are painting it with the same paint.
- Set coats and coverage, then read the gallons and cans to buy.
Worked examples
A 14 × 12 ft bedroom with 8 ft walls, one door and two windows, two coats
- Area to paint (one coat)
- 365 ft²
- Paint needed
- 2.09 gal
- Gallon cans to buy
- 3
- Paint cost
- $105.00
A 10 × 10 ft room including the ceiling, two coats at 400 sq ft per gallon
- Area to paint (one coat)
- 384 ft²
- Paint needed
- 1.92 gal
- Gallon cans to buy
- 2
- Paint cost
- $70.00
Coverage per gallon
Most interior paints cover 350–400 sq ft per gallon on smooth, primed walls. Expect closer to 250–300 on fresh drywall, textured walls, bare wood or masonry, which soak up more.
Two coats is the norm, especially over a different color. A primer coat counts separately and usually covers 200–300 sq ft per gallon.
Trim and ceilings
Ceilings normally get flat ceiling paint, so calculate them on their own if you are using a different product. Trim, doors and baseboards take surprisingly little: a quart of trim paint covers about 90–100 sq ft.
Questions people ask
How much paint do I need for a 12×14 room?
With 8 ft walls, one door and two windows there are 365 sq ft of wall. Two coats at 350 sq ft per gallon need 2.09 gallons, so buy 3 gallons, or 2 gallons and a quart.
How many square feet does a gallon of paint cover?
About 350–400 sq ft per coat on smooth, primed surfaces.
Do I really need two coats?
Usually yes. One coat rarely hides the old color evenly, and the second coat gives the sheen and durability the paint is rated for. One coat can be enough when repainting in the same color with a quality paint.