Paint Calculator: How Much Paint for Your Room?
Calculate how many gallons of paint you need. Covers walls, ceilings, trim, and multiple coats.
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Use BriskTool's free tool for this task
One gallon covers roughly 350-400 square feet. But how many square feet are your walls? And how many coats do you need? Here's how to figure it out without buying too much or too little.
Quick Method
Measure the perimeter of the room (add all wall lengths together). Multiply by the ceiling height. Subtract windows and doors. That's your paintable square footage.
Divide by 350 for one coat. Most rooms need two coats, so divide by 175 instead.
Use the Calculator
The Paint Calculator handles all of this. Enter room dimensions, number of windows and doors, number of coats, and whether you're painting the ceiling. Get a shopping list with exact gallon counts.
Do You Need Primer?
Yes if: The walls are new drywall, you're going from dark to light color, you're painting over stains, or the surface has never been painted.
No if: You're painting the same color or going slightly darker, the existing paint is in good condition, and you're using paint-and-primer-in-one.
Buying Tips
Buy the next size up. If you calculate 1.3 gallons, buy 2. You'll need the extra for touch-ups later, and most stores don't take back custom-mixed paint. The leftover is cheap insurance.