Find the surface area
Enter the total area of the walls, ceiling, or other surfaces you plan to paint. If you do not know the area yet, use the Square Footage Calculator first.
Surface area = total area to measure
Paint & walls
Paint Calculator
Estimate how much paint you need based on the area you are painting, openings to exclude, number of coats, coverage per can, and paint price.
Calculation method
How to calculate how much paint you need
Start with the total surface area, subtract doors, windows, or other areas that will not be painted, multiply by the number of coats, then use the paint manufacturer's coverage rate to estimate how many cans to buy.
Subtract doors and windows
Remove the area of openings or other sections that will not receive paint.
Paintable area = surface area − excluded area
Account for the number of coats
Multiply the paintable area by the number of coats you plan to apply.
Coverage needed = paintable area × coats
Calculate cans and cost
Divide the required coverage by the coverage listed on one can and round up. If you enter a price, the calculator also estimates the paint purchase cost.
Cans = coverage needed ÷ coverage per can
Worked example
Suppose your walls have a total surface area of400 ft², but doors and windows account for40 ft². That leaves360 ft² of paintable area.
With 2 coats, the project requires720 ft² of total paint coverage.
If one can covers 350 ft², then 720 ÷ 350 is about 2.06, so you would need to round up to3 cans.
At $45 per can, the estimated paint cost is$135.
How many coats of paint do you need?
- 1 coat — may be enough for touch-ups or some similar-color repainting projects.
- 2 coats — a common choice for many interior and exterior painting projects.
- 3 coats — may be needed for major color changes, difficult surfaces, or when specified by the paint manufacturer.
Primer requirements and actual coat recommendations vary by surface, paint product, color, and manufacturer.
Paint calculator FAQ
How do I calculate how much paint I need?
Calculate the surface area, subtract areas that will not be painted, multiply by the number of coats, then divide by the coverage provided by one can of paint.
Should I subtract doors and windows?
Yes, if you want a more precise estimate. Enter their combined area as the excluded area so it is removed before the number of coats is applied.
How much area does one can of paint cover?
Coverage varies by product and surface. Use the coverage rate printed on the specific paint container or manufacturer information rather than relying on a universal value.
Does the paint calculator include primer?
No. This calculator estimates paint only. Primer should be calculated separately when your project requires it.
What this estimate assumes
- The surface area you enter is accurate.
- Excluded areas are contained within the measured surface.
- The number of coats matches your planned project.
- Coverage per can matches the specific paint product you plan to purchase.
- Paint quantities are rounded up to complete containers.
- Estimated cost is based only on the price per can you enter.
Before purchasing: verify coverage, coat recommendations, primer requirements, container size, and surface preparation instructions provided by the manufacturer.