Use the paint can label for coverage because deep colors, textured walls, and primer can change the number.
Interior walls
Paint Calculator
Enter the room size, openings, coats, and coverage rate to estimate how much paint to buy before you head to the store.
Example estimate ready.Change the measurements and product prices below. Values save only on this device.
Calculation method
How the estimate is built.
We calculate the perimeter wall area, remove the square footage of doors and windows, then multiply by coats and your extra buffer before dividing by the coverage on the paint can.
Field notes
Use the estimate well.
Round up to a full gallon if you want touch-up paint from the same batch.
Subtract large doors and windows, but do not worry about tiny trim openings.
FAQ
Paint questions
How much area does one gallon of paint cover?
Many interior paints cover about 300 to 400 square feet per gallon, but the exact number depends on the product, wall texture, color change, and application method.
Should I include a waste buffer?
Yes. A 10 percent buffer is a practical starting point for roller loss, touch-ups, and small measurement mistakes.
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