Paint Calculator
Your estimate
- Area to paint
- 334 ft²37.11 yd² · 31.03 m²
- Estimated cost
- $76.34
Walls (and the ceiling if you like) minus doors and windows, times the number of coats.
Updated 2026-10-20 · Based on: coverage figures from paint and drywall makers (USG).
How to use the Paint Calculator
- Enter the room length, width and wall height.
- Type the number of doors and windows.
- Choose 2 coats for a colour change, 1 for a refresh.
- Check the coverage on your can (350–400 ft² per gallon is typical) and read the gallons.
Formula
Wall area = 2 × (length + width) × height − 20 ft² per door − 15 ft² per window.
Gallons = area × coats ÷ coverage per gallon. Metric: litres = m² × coats ÷ m² per litre (about 10).
Worked example
With the values preset in the calculator above:
- Length
- 12 ft
- Width
- 12 ft
- Wall height
- 8 ft
- Doors
- 1
- Windows
- 2
- Include ceiling
- No
- Coats
- 2
- Coverage per coat
- 350 ft² per gallon
- Paint needed
- 1.9 gal (7.2 L)
- Area to paint
- 334 ft² (37.11 yd²)
- Estimated cost
- $76.34
How much paint do I need for a room?
A 12 × 12 ft room with 8 ft walls, one door and two windows has 334 ft² of wall. Two coats at 350 ft² per gallon take 1.9 gal — buy 2 gallons. Add one more gallon if you also paint the ceiling.
Frequently asked questions
How many square feet does a gallon of paint cover?
About 350–400 ft² per coat on smooth, primed walls; 250–300 ft² on rough or porous surfaces.
How much paint for a 10 × 10 room?
With 8 ft walls, one door and one window and two coats: about 1.6 gal.
Do I need primer?
Yes on new drywall, bare wood, stains or a big colour change. Primer covers about 200–300 ft² per gallon.
More calculators
Estimates only — check quantities with your supplier and local building code before you order.