Construction & Home
Paint Calculator
A paint calculator estimates paint quantity from room wall area, number of coats, and coverage per gallon or liter, with optional waste allowance.
Quick answer
Calculates net wall area after subtracting doors/windows.
What this tells you
- •Calculates net wall area after subtracting doors/windows.
- •Applies number of coats and coverage rate.
- •Adds waste allowance to estimate total paint to buy.
How to Use
- 1Enter room length, width, and wall height.
- 2Set coats and paint coverage rate.
- 3Subtract non-paint areas such as doors and windows.
- 4Set waste percentage and calculate.
How It Works
Formula
Wall area = perimeter x wall height - non-paint area
Paint needed = (wall area x coats / coverage) x (1 + waste%)Perimeter-based wall area is multiplied by coats and adjusted by coverage and waste assumptions.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Bedroom estimate
Room12x10 ft
Height8 ft
Coats2
Coverage350 ft2/gal
Waste10%
ResultEstimated gallons and liters required
Common mistakes
- Ignoring doors/windows
- Using coverage from wrong paint type
- Skipping waste allowance
Frequently Asked Questions
Yes. Enter total non-paint area to subtract openings.
It estimates paint calculator outputs using the visible inputs and formula assumptions on this page.
Results are calculation estimates based on your inputs and stated assumptions. Verify values for critical decisions.