Paint Calculator Guide
Estimate paint from wall surface area, openings, coats and the coverage stated by the paint manufacturer.
Open calculatorMeasure first. The formula does the rest.
Use consistent units for every measurement. Keep the original values precise; only round the final quantity you plan to buy.
See the calculation change
This is an interactive example, not a replacement for checking the material manufacturer's specifications.
How the calculation works
Paint = ((Wall area − Openings) × Coats) ÷ Coverage
Measure wall length and height and multiply by the number of walls.
Subtract the area of doors and windows.
Multiply by coats and divide by the manufacturer's coverage.
Before you buy
- ✓Use the coverage printed on the exact paint product whenever possible.
- ✓Primer, porous surfaces and texture can change real coverage.
- ✓Keep the same paint batch where colour consistency matters.
Common questions
Why does coverage matter so much?
Coverage differs between products and surfaces. Using the manufacturer's figure gives a more useful estimate than a hidden generic assumption.
Should doors and windows be subtracted?
Yes, if you know their combined area. The calculator prevents that area from being painted twice in the estimate.
Does it include primer?
No. Treat primer as a separate material unless you are using a product designed as paint-and-primer.