Paint Calculator — Gallons, Liters, Cans & Cost
Estimate paint for rooms, walls, and ceilings. Subtract doors and windows, set coats and coverage, and see gallons or liters, cans, leftover paint, and cost.
Measure a room
Walls are calculated from room length, width, and height. Add the ceiling when it will use the same paint.
Subtract doors and windows
Use typical opening sizes or enter an extra deduction for built-ins and other unpainted areas.
Paint and purchase details
Use the coverage printed on the can. Rough or porous surfaces usually need more paint.
Project view
Estimate breakdown
| Gross surface | |
| Doors and windows | |
| Net paintable area | |
| Coverage for all coats | |
| With waste / touch-ups | |
| Purchased volume | |
| Paint left over |
How the estimate is calculated
How much paint do I need?
Measure each wall or use room length, width, and height. Subtract doors and windows, multiply the paintable area by the number of coats, then divide by the coverage shown on your paint can.
Paint coverage per gallon
Many interior paints cover about 350–400 square feet per US gallon for one coat. Coverage varies by paint, color change, surface texture, porosity, and application method, so the product label is the best source.
Paint cost calculator
Select the container size sold by your paint brand and enter its price. The estimate rounds up to whole cans and shows purchased volume, expected leftover paint, and total material cost.
Gallons, liters, coats, and waste
Switch between US and metric units without losing the project. Two coats are common for durable, even coverage. A 5–10% allowance helps with roller loss, touch-ups, and small measurement errors.
