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.
Finished surface you can cover
This is actual painted surface, not room floor area. Coverage varies with the product and surface; use the rate on your tin. US gallons are used in US mode.
From measured area to paintable surface
352 sq ft measured area
- To paint
- 307 sq ft · 87.2%
- Doors
- 21 sq ft · 6.0%
- Windows
- 24 sq ft · 6.8%
Segments show area shares, not the position or shape of doors and windows. Paint quantity also includes coats and the selected allowance.
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. For several rooms, calculate the paintable wall surfaces for each room and add them together before using Known area mode. Floor area is not wall area. The square footage calculator can help total measured rectangular surfaces; enter the width and height of the surfaces you will paint, not the floor dimensions.
Painting a board-and-batten wall
Plan strip positions with the board and batten spacing calculator. For paint quantity, measure the exposed wall and timber faces plus any exposed sides or edges. Avoid counting the covered wall behind each batten twice; primer and finish coats may have different coverage rates.
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
To calculate the surface you can cover with paint you already own, choose I have paint. Divide volume × label coverage by coats × (1 + allowance/100). For example, 750 ml at 12 m²/L covers 4.5 m² with two coats and no allowance, or about 4.09 m² with 10% allowance. This is an example rate, not a guarantee for every tin. 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.
How much paint does 1 quart cover?
At a label rate of 400 sq ft per gallon, one US quart covers about 100 sq ft for one coat or 50 sq ft for two coats, before waste. At 350 sq ft per gallon, the same quart covers about 87.5 sq ft for one coat. Use the product label for the actual paint and surface.
How many gallons for 2,000 sq ft?
At 400 sq ft per gallon, 2,000 sq ft needs 5 gal for one coat, 10 gal for two coats, or 11 gal for two coats plus 10% allowance. A practical 11-gallon purchase can be two 5-gallon pails plus one 1-gallon can when the same product and batch are available.
Cabinets and doors need measured surface area
Do not treat every cabinet or door as one fixed unit. Measure paintable faces, backs, edges, frames, drawer fronts, and end panels, then use Known area mode. The 250 sq ft cabinet preset needs 1.38 gal for two coats with 10% allowance at 400 sq ft/gal.
Installing new wall panels first? Use the drywall sheet calculator to plan separate wall and ceiling panel orders before estimating paint.
