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Paint Calculator by Square Feet
Already know the square footage? Type it in with the coats, the coverage on the can and a waste allowance. You get the gallons, the amount to buy to the nearest quart, the cost and the cost per square foot. 850 sq ft with two coats and 10% extra needs 5.3 gallons.
Updated · Sources re-checked by
Coverage per gallon (check the can)
5.34 gallons
| Paint to cover | 1,870 sq ft |
| To the nearest quart | 5.5 gallons |
| Whole gallons | 6 |
The coverage on your can wins over any preset. You can type 850, 850.5 or 1,000. Nothing you type is saved or sent anywhere.
How paint is calculated from square feet
Paint to cover = area × coats × (1 + waste ÷ 100). Gallons = paint to cover ÷ coverage per gallon (350 sq ft is a cautious figure for smooth interior walls, and the can's label wins). Quarts to buy = gallons rounded up to the next quarter gallon. Whole gallons to buy = gallons rounded up. Cost = gallons bought × price per gallon, and cost per square foot = cost ÷ area.
| Area | One coat | Two coats |
|---|---|---|
| 250 sq ft | 0.71 | 1.43 |
| 500 sq ft | 1.43 | 2.86 |
| 1,000 sq ft | 2.86 | 5.71 |
| 2,000 sq ft | 5.71 | 11.43 |
| 3,000 sq ft | 8.57 | 17.14 |
| Coverage per gallon | Gallons |
|---|---|
| 250 sq ft | 4 |
| 300 sq ft | 3.33 |
| 350 sq ft | 2.86 |
| 400 sq ft | 2.5 |
Worked example: 850 sq ft, two coats, 10% extra, $40 a gallon
- Two coats: 850 × 2 = 1,700 sq ft of paint to cover.
- Add 10% for waste and touch-ups: 1,700 × 1.10 = 1,870 sq ft.
- Gallons: 1,870 ÷ 350 = 5.34.
- To the quart: 5.5 gallons, which is 5 gallons and 2 quarts.
- Buying whole gallons: 6 × $40 = $240.00, about $0.28 per square foot.
Common questions
How do I calculate paint from square feet?
Multiply the area by the number of coats and divide by the coverage on the can. For 850 sq ft, two coats and 350 sq ft per gallon, that is 1,700 ÷ 350, about 4.9 gallons before waste.
How many square feet does a gallon of paint cover?
General guides give about 350 to 400 sq ft per coat for smooth interior walls. Glossy paint, rough walls and dark colors can cover less. Always use the figure on your can if it differs.
Where do I get the area?
For walls, multiply the room's perimeter by its height and take off the doors and windows. If you want the room-by-room version, use the paint calculator that works from room sizes.
How much waste should I allow?
Five to ten percent is common, for spills, the roller and touch-ups. Set it to zero if you want the exact figure.
Should I buy quarts or gallons?
If the leftover is small, a quart can cost less than another gallon, and some stores sell by the quart. Compare the price per gallon before you decide.
Does primer count as a coat?
Primer is a separate product with its own coverage. If you will prime and paint twice, add it as a coat or run the area through the calculator again with the primer's coverage.
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Sources
- How much area does a gallon of paint cover: about 350 to 400 sq ft per coat; the can's label is the real figure (checked October 28, 2026)
This calculator is an estimate for planning. Coverage depends on the paint, the surface and how you apply it, so check the can and ask the paint store before you buy.