Paint Calculator

Gallons (or quarts) of paint for a room. Standard 350 sqft per gallon coverage, doors and windows deducted, rounded up so you don't run out mid-wall.

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Gallons (rounded up)

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Or in quarts

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Raw amount needed

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Paintable wall area

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Total sqft × coats

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The 350-sqft-per-gallon rule

That's coverage for one coat on average wall texture with average roller technique. Variables that move the number:

  • Porous surfaces (new drywall, textured ceilings): coverage drops to ~250 sqft/gal — prime first or buy more.
  • Sprayer: more overspray, coverage ~300 sqft/gal.
  • Glossy / specialty paints: often 250–300 sqft/gal listed on the can.

Why round up to the nearest quart

Paint cans come in quarts and gallons. If you need 1.6 gallons, you need to buy 2 gallons or 1 gallon + 3 quarts. Buying a hair too little means stopping mid-job to make a hardware store run with a wet roller in hand. Buying a hair too much means saving leftover for touch-ups.

Standard deductions

Door = 21 sqft (3' × 7'). Window = 15 sqft (3' × 5'). These are averages — most paint calculators (Sherwin-Williams, Behr) use the same figures.

Buy primer separately

If you're going light over dark, prime first. Two coats of paint over white drywall almost always works; two coats of pale paint over a deep red almost never does.