Paint calculator: how much paint, and the cheapest cans to buy
Enter your rooms, coats and the coverage on the can. We work out the paint you need and the cheapest combination of quarts, gallons and 5-gallon buckets at the prices you see in store.
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Assumptions
- Wall area is the room perimeter × wall height, minus each door and window.
- Paint needed = area × coats ÷ the coverage printed on the can.
- With prices for every can size we pick the cheapest mix; without prices, the mix with the least left over.
Why the can mix matters
Paint is sold in fixed sizes and the price per gallon changes with the size. For 2.3 gallons, two gallons and two quarts may cost less than three gallons, or more, depending on the store. A 5-gallon bucket is cheaper per gallon, but only if you use most of it. This planner checks every combination of the sizes you enter and shows the cheapest one.
How to measure for paint
- Measure the length and width of the floor and the height of the walls.
- Count the doors and windows. Large openings like sliding doors can be entered as two doors.
- Tick "Paint the ceilings too" if they get the same paint.
- Check the coverage on the can: it is usually given per gallon or per liter, per coat.
Frequently asked questions
How much paint do I need for a room?
Multiply the room perimeter by the wall height, subtract doors and windows, multiply by the number of coats and divide by the coverage on the can. Most interior paints cover about 350 to 400 square feet per gallon per coat.
Is it cheaper to buy a 5-gallon bucket?
Often, but not always. A 5-gallon bucket usually costs less per gallon, but if you only need 3 gallons the leftover can cost more than it saves. This calculator compares every mix of can sizes at your prices.
How many coats of paint do I need?
Two coats is the usual recommendation for even color, especially over a different color or new drywall. One coat can be enough for a fresh coat of the same color with a quality paint.
Should I subtract doors and windows?
Yes. A typical interior door is about 21 square feet and a window about 15 square feet. You can change both values in the calculator.