HOMEQIA Paint Calculator
Enter your room's dimensions and get a recommended number of paint gallons — accounting for doors, windows and how many coats you need.
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Tell us about your room
Wall height matters as much as floor size here. Switch units any time.
A few more details
Doors and windows don't get painted, so we'll subtract them.
Paint Needed
This is a recommended starting estimate based on standard door/window sizes and typical paint coverage — actual coverage varies by paint brand, wall texture and color change. Always check the coverage listed on your specific paint can.
How This Calculator Works
Paint quantity comes down to one number: total paintable wall area. This calculator finds that by multiplying your room's perimeter by the wall height, then subtracting standard allowances for doors (about 21 sq ft each) and windows (about 15 sq ft each). From there, it divides by a typical coverage rate of 350 sq ft per gallon, per coat, and rounds up — since running short mid-project is a bigger problem than having a little extra.
Why Coverage Estimates Vary
The 350 sq ft per gallon figure is a reasonable average, but actual coverage depends on your specific paint brand, the wall's texture, and how big a color change you're making. A heavily textured wall or a dramatic color shift (dark to light, or the reverse) can reduce real coverage meaningfully, sometimes requiring a third coat in high-contrast spots. Always check the coverage number printed on your specific can before finalizing how much to buy.
Planning the Rest of the Room
If you're repainting as part of a bigger refresh, our guide on choosing a color palette for your home covers how to pick a palette that works with existing furniture and flooring, not just the wall in isolation. And if new furniture is part of the plan too, the free HOMEQIA Smart Room Planner can help size it for the same room.
How many gallons of paint do I need for one room?
It depends on your wall area and how many coats you're applying, but as a rough reference, an average 12×15 ft bedroom with 8 ft ceilings typically needs about 3 gallons for two coats, accounting for one door and one window.
Do I really need two coats of paint?
For a color change or a wall going from dark to light, yes — two coats are standard for even, opaque coverage. A single coat is usually only enough for a touch-up or repainting the exact same color.
How much wall area does one gallon of paint cover?
Most paint brands cover roughly 350–400 sq ft per gallon, per coat, on a smooth wall. Textured walls, unprimed drywall, and very light-to-dark color changes typically reduce real coverage, so checking your specific can's label is worth doing before buying.
Should I round up or down when buying paint?
Always round up. Paint is far easier to store leftover than to run out of mid-project and try to color-match a new can, especially with a custom-tinted color.