Paint Calculator
Estimate gallons of paint from wall width, height, coats, and coverage.
How this tool works
Estimate paint quantity before buying supplies for a room or wall project. CasaLabs calculators keep assumptions visible, use source-backed formulas, and avoid storing personal information.
How to use it
- Measure the wall width and height in feet.
- Enter the number of coats and the paint coverage listed on the can.
- Use the waste allowance to account for texture, touch-ups, and measuring error.
Formula
Gallons = wall width × wall height × coats × (1 + waste percent) ÷ coverage per gallon.
Example
A 40 ft by 10 ft wall with 2 coats, 10% waste, and 400 sq ft/gallon coverage needs 2.2 gallons, so you would round up to 3 gallons.
Common mistakes
- Forgetting the second coat.
- Using the room floor area instead of wall area.
- Ignoring lower coverage on textured or porous surfaces.
Assumptions
- Wall area is calculated as width multiplied by height.
- Paint coverage is entered as square feet per gallon.
- The estimate rounds up to whole gallons for shopping.
- A waste allowance helps account for texture, touch-ups, and measuring error.
Sources
Related calculators
FAQ
How do I calculate how much paint I need?
Multiply wall width by wall height, multiply by the number of coats, add any waste allowance, then divide by the paint coverage per gallon.
Why does the calculator round up?
Paint is normally purchased by container size, so rounding up helps avoid running short during the project.