Paint Calculator
How many gallons to paint a room — coats, doors, and windows included.
Your estimate
Estimates only. Renovate Cafe's calculators are a planning aid, not professional advice — double-check your inputs, confirm coverage on the product you buy, and verify quantities and local code for structural, electrical, or permitted work. Disclaimer.
Enter your room's dimensions, how many coats, and how many doors and windows to skip. Renovate Cafe subtracts the openings, multiplies by coats, and tells you how many gallons to buy — rounded up to whole cans.
How much paint do I actually need?
Start with the walls: the perimeter of the room (two times length plus two times width) multiplied by the ceiling height gives the gross wall area. Then subtract the openings — a standard door is about 21 square feet and an average window about 15 — because you're not painting those. That leaves the paintable area.
Multiply the paintable area by the number of coats, then divide by the coverage printed on the can (usually 350–400 square feet per gallon). The result is your raw gallon figure; the calculator rounds it up to whole cans, because that's how paint is sold.
Primer, coats, and color changes
Two coats is the honest default for a durable, even finish. You can sometimes get away with one coat of a quality paint-and-primer over a similar color, but big color changes, new drywall, and going light-over-dark almost always want a primer coat plus two finish coats. When in doubt, buy the rounded-up amount — a little leftover for touch-ups beats a second trip to the store mid-job and a slightly different mixed batch.
If you're painting the ceiling, flip the toggle and the calculator adds the ceiling area (length × width) to the first coat's total.
Frequently asked questions
How many gallons of paint for a 12x14 room?
Does one gallon of paint do two coats?
Do I need primer?
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