DIY & Home · Quick Answer
How much paint do I need?
One gallon covers about 350 square feet with one coat. To paint a room: measure wall square footage (perimeter × height), subtract doors/windows, multiply by number of coats, divide by 350.
The standard formula
Gallons = (wall area × number of coats) / 350
Where wall area = perimeter × ceiling height, minus doors and windows.
Example: 12 × 14 ft room, 9 ft ceilings, 2 coats
- Perimeter: (12 + 14) × 2 = 52 ft
- Wall area (gross): 52 × 9 = 468 sq ft
- Subtract 1 door (~21 sq ft) and 2 windows (~30 sq ft): 468 − 51 = 417 sq ft
- Two coats: 417 × 2 = 834 sq ft
- Gallons: 834 / 350 = 2.4 gallons → round up to 3
Coverage by surface type
- Smooth drywall / previously painted: 350 sq ft/gallon
- Textured or porous drywall: 250-300 sq ft/gallon
- Bare wood or masonry: 200 sq ft/gallon (plus a primer coat)
- Rough stucco, brick: 150-200 sq ft/gallon
When you need a primer
- New drywall or bare wood
- Dramatic color change (dark → light especially)
- Patch repairs
- Stain blocking (water damage, smoke)
Self-priming paint saves a coat on small projects but still benefits from a proper primer on challenging substrates.
Don't forget
- Ceilings, same formula, but ceilings often need only 1 coat of flat paint
- Trim, a quart usually covers the trim in a single room
- 10% waste buffer for spills, drying, touch-ups