How this calculator works
Estimate a practical paint quantity before you buy. The calculator subtracts openings, applies the number of coats, adds a waste allowance and rounds the result into purchase-friendly gallons.
Paintable wall area = perimeter × wall height − door area − window area. Gallons = area × coats × (1 + waste) ÷ coverage.
Example
A 12 × 10 ft room with 8 ft walls, one door, two windows and two coats needs about 2–3 gallons at typical coverage.
How to get a better estimate
- Measure each room instead of estimating from floor area alone.
- Use the coverage printed on the specific paint can whenever possible.
- Add more waste for textured walls, color changes or porous surfaces.
What the result means
The result is a planning estimate. Dimensions, coverage, density, packaging and installation conditions vary by product and project. For purchasing, compare the result with the exact product label or supplier specification. For structural, electrical, code-regulated or safety-critical work, use an appropriately qualified professional.
Common questions about the Paint Calculator
What does this calculator estimate?
Estimate a practical paint quantity before you buy. The calculator subtracts openings, applies the number of coats, adds a waste allowance and rounds the result into purchase-friendly gallons.
What formula does it use?
Paintable wall area = perimeter × wall height − door area − window area. Gallons = area × coats × (1 + waste) ÷ coverage.
How should I use the result?
Use it as a planning estimate, then verify the dimensions and replace editable defaults with the specifications for the product or service you actually intend to buy.
Reference tables
Want a fast benchmark without changing inputs? These static tables use the same published calculation method.