How do I calculate gallons of paint for a room?
Gallons = ((wall area − openings + optional ceiling) × coats) ÷ coverage per gallon, rounded up for purchase.
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Paint calculator
Estimate paint by room or wall, including openings, coat count, and coverage rate.
- Metric and imperial units
- Instant updates as inputs change
- Data is calculated in this browser only
Results are planning estimates. Confirm site dimensions, product specifications, and installation waste before purchasing.
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Calculation notes
Understand the Paint calculator
Wall area is 2 × (room length + width) × ceiling height, less doors and windows. If selected, ceiling area is length × width. Net area is multiplied by coat count and divided by the chosen paint coverage.
How much paint is needed for a 12 by 10 ft room with two coats?
A 12 × 10 ft room with 8 ft walls has 352 sq ft of wall area. After 51 sq ft of doors and windows, two coats cover 602 sq ft; at 350 sq ft/gal, buy 2 gallons before any added waste.
Should doors and windows be subtracted from paintable wall area?
- Round to purchasable can sizes after comparing one- and five-gallon pricing.
- Use the manufacturer’s label coverage when it differs from the default.
Why can actual paint coverage differ from the label estimate?
- The estimate uses U.S. gallons and common coverage per gallon.
- Color changes, rough surfaces, and application loss can increase actual use; verify the product label.
- Porous surfaces, dramatic color changes, spraying, and touch-ups can increase use.
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