Home & Household
Enter your room's dimensions to find out how many gallons of paint you need and roughly what it'll cost.
Last updated: August 2026
Wall area is the room's perimeter times wall height, minus a standard allowance for doors and windows. That area is multiplied by your number of coats, then divided by your paint's coverage rate to get gallons — rounded up, since paint only comes in whole cans.
Coverage varies by paint brand, wall texture, and color change (a big color shift often needs an extra coat) — check your specific can's label if you have it.
Common questions about paint coverage, coats, and buying the right amount.
Two coats is the standard for most interior wall paint jobs, and what this calculator assumes by default. You may only need one coat if you're repainting a wall the same or a very similar color. You'll typically need three or more if you're covering a dark color with a much lighter one, painting a bold accent color, or using a lower-quality paint with weaker pigment.
The area formula is different — ceilings are calculated as length × width rather than perimeter × height, since you're covering a flat overhead surface rather than four walls. You can still use this calculator for a ceiling by entering the ceiling's length and width as the 'room length' and 'room width' fields and setting wall height to 1, then adjusting doors/windows to zero.
The most common reasons are textured or porous walls (like new drywall or stucco) soaking up more paint than the can's stated coverage, a color change requiring an extra coat you didn't budget for, or simply underestimating trim and edges that get extra touch-up coats. When in doubt, round up to the next full gallon rather than buying the bare minimum.
It's generally safer to round up and buy a little extra, both to cover the reasons above and to have leftover paint for future touch-ups — since paint colors are sometimes discontinued or hard to match exactly later. Keeping a labeled, sealed can of leftover paint is cheaper than a repeat trip to the store.
Yes, significantly. Smooth, previously painted drywall is close to the coverage rate listed on the can. Textured surfaces (orange peel, knockdown, stucco, brick) can reduce effective coverage by 20-30% or more because paint fills in the texture rather than just coating a flat plane. If your walls are textured, consider lowering your coverage-per-gallon input to account for it.
