Home and property
Paint calculator
Measure around the room and the wall height in feet. Doors and windows are subtracted using typical sizes. Coverage comes from your paint can's label.
What this means
- 333.0 square feet of wall at 2 coats needs 1.90 gallons, so buy 2.
- That is about $80.00 in paint before primer and supplies.
- Ceilings are not included. Measure them as length times width and run them separately.
What if
About this calculator
What this calculator does
It finds the wall area, subtracts doors and windows, multiplies by the number of coats, and divides by the coverage per gallon.
How it is calculated
wall area = total wall length * height
paintable area = wall area - doors * 21 - windows * 15
gallons = paintable area * coats / coverage, rounded up
How to read the result
Gallons to buy is rounded up to a whole can. The exact figure helps if you can buy quarts for the remainder.
Assumptions
A door is counted as 3 by 7 feet (21 square feet) and a window as 3 by 5 feet (15 square feet). Large openings should be measured and subtracted from the wall length instead.
Sources and method
Standard arithmetic with no outside data. The formula is shown under How it is calculated, and unit tests check worked examples, including edge cases.
This page uses arithmetic only, with no outside data.
Questions
How much does a gallon cover?
It is printed on the can. Coverage depends on the product and the wall surface.
Do I need two coats?
Often, especially for a color change. One coat may be enough for the same color in good condition.
Does it include primer?
No. Run the calculator again with the primer's coverage if you need it.
How do I handle a ceiling?
Multiply the room's length by its width for the ceiling area, then divide by coverage per coat.