Room paint calculator
How much paint for this room?
Enter your room's dimensions, ceiling height, and the number of doors and windows — we'll subtract the openings and tell you how many gallons to buy.
Enter your room
We assume 350 sq ft of coverage per gallon (a typical mid-grade interior/exterior paint) — check your can's label and adjust if it differs.
Results
- Area to paint
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- Paint needed
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- Gallons to buy
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- Estimated cost
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Rounded up to whole gallons — paint stores don't sell partial cans.
Estimates only — check your paint's actual coverage rate on the can before buying.
How it's calculated
Perimeter × height, minus openings.
We find your room's perimeter (2 × length + width), multiply by ceiling height to get gross wall area, then subtract a standard allowance for each door and window you enter. The remaining net area is multiplied by your number of coats and divided by the coverage rate to get gallons.
FAQ
Common questions
Does this include the ceiling?
No — this estimates wall paint only (perimeter × height, minus doors and windows). If you're painting the ceiling too, run its area separately through the paint calculator using its own coverage rate.
How much area does a door or window take off?
We subtract 20 sq ft per standard door and 15 sq ft per standard window from the gross wall area. Oversized openings (sliding doors, bay windows) will take off more — adjust your inputs if yours are unusual.
Should each wall get a different number of coats?
Not usually — most rooms get the same number of coats throughout for a consistent finish. An accent wall in a different color still typically gets two coats of its own paint.
What if my room isn't rectangular?
Enter the room's overall length and width as if it were rectangular — for an L-shaped or irregular room, break it into two rectangular sections and run each through the calculator separately, then add the results.