Calculator guide
Estimate paint quantity from wall dimensions, coverage, coats, and openings.
Formula or method
Paint gallons = paintable area × coats ÷ coverage per gallon; subtract openings when known, then round up.
How to use this calculator
- Enter wall dimensions and the number of coats.
- Enter coverage from the paint label.
- Subtract doors or windows if supported and review gallons.
Worked example
A 400 ft² paintable area needing two coats at 350 ft²/gal requires 800/350=2.29 gallons, so buy 3 gallons.
Understanding the result
Label coverage is a best-case figure; texture, primer, color changes, and application can increase use.
Limitations and assumptions
- Ceilings, trim, porosity, and waste may require separate calculations.
- Coverage varies by product and surface preparation.
Frequently asked questions
Does primer count as a coat?
It uses material, but its coverage and purpose may differ from finish paint.
Why round up?
Buying a little extra helps maintain a consistent color and finish.
Can I mix leftover cans?
Only if the product and color are compatible; follow the manufacturer's guidance.
Sources
Educational information only; verify important decisions with a qualified professional.