Work out how much paint to buy for a wall, a room or walls plus a ceiling. Set the actual per-coat coverage and container size, then see how allowance and container rounding change the order.
Plan coats and whole containers from your product’s per-coat coverage.
Read the product label; use a lower rate for rough or porous surfaces.
Use one currency throughout; tax, labor and delivery excluded.
Prices use your chosen currency consistently. Blank price skips cost. Example coverage, density, yield and prices are editable scenarios, not current product offers.
Illustration is schematic, not an installation drawing.
| Net surface | 312 ft² |
|---|---|
| Coat-area | 624 ft² |
| Paint with allowance | 1.96 US gal |
| Purchase volume | 2 US gal |
| Left after estimate | 0.04 US gal |
| Material cost | Not entered |
Method: (Surface − openings) × coats × (1 + allowance/100) ÷ coverage, rounded up to whole containers.
Coverage is per coat. Primer, trim and surface-specific absorption are excluded. Ceiling uses the same paint and coat count in this scenario.
Quantity and material-only cost estimate. Verify field measurements, product instructions and your purchase units. Labor, delivery, taxes, equipment and structural adequacy are excluded.
Calculations run in your browser. This tool does not request a location, retrieve live prices or send your measurements to a material supplier.
Choose one wall, four room walls, or room walls plus ceiling. Enter length, width and wall height in the selected system.
Subtract the measured area of unpainted openings. Enter the number of coats, label coverage per coat, container size and added allowance.
Optionally enter a price per container. Compare required paint with purchased paint, then copy or download the estimate.
A 12 × 10 ft room with 8 ft walls has 352 ft² of wall surface. Subtract 40 ft² of openings to get 312 ft². At two coats, 350 ft² per US gallon and 10% allowance, the requirement is about 1.96 US gallons: buy two 1-gallon containers.
The same room adds 120 ft² when the ceiling is included. The net surface becomes 432 ft²; with the same paint assumptions, the quantity becomes about 2.72 US gallons, rounded to three containers.
Behr explains that perimeter multiplied by wall height gives wall area, and that surface texture and color changes affect paint demand. Use the coverage range and coat instructions for your chosen paint. The example value here is a scenario, not a guarantee for a brand or finish.
The calculator uses one container size for the whole order. It does not compare a mixture of quarts, gallons and large pails. Primer and trim usually need separate estimates because their coverage and products can differ. If the ceiling uses a different finish, calculate it separately.
Enter coverage for one coat and put the coat count in its own field. Multiplying twice by a two-coat coverage figure would overestimate demand.
Dimensions, area, coverage and paint volume are converted. US liquid gallons convert to liters. Container price remains the price of that same physical container.
You can enter their combined measured area. Small openings may not save as much paint as their geometric area because cutting-in and application losses vary.