Estimate paint by dividing the wall area by the coverage per gallon, multiplied by the number of coats, then rounding up to whole gallons. No more guessing at the store.
The example
800 sq ft, 2 coats, 350/gal.
| A | B | |
|---|---|---|
| 1 | Item | Value |
| 2 | Area × coats | 1600 |
| 3 | ÷ 350/gal | → 5 gal |
The formula
The formula:
How it works
How it works:
- Coverage per gallon is on the can — typically 350–400 sq ft for one coat.
- Multiply area × number of coats, then divide by coverage.
ROUNDUP(…, 0)rounds to whole gallons (or buy the next can size).- Subtract large openings (doors, big windows) from the area first for a tighter estimate.
Primer and texture change the math. Bare drywall or a dark-to-light change often needs a primer coat (count it as an extra coat). Rough or textured surfaces drink more paint — drop the assumed coverage to ~300 sq ft/gal. When in doubt, round generously; a touch-up gallon is cheap insurance.
Try it: interactive demo
Area, coats, coverage per gallon.
Variations
Net of openings
Subtract doors/windows:
Add primer coat
Count it:
Paint cost
Gallons × price:
Pitfalls & errors
Coats matter. Two coats doubles the paint — don’t forget the multiplier.
Texture eats paint. Lower the coverage assumption for rough surfaces.
Round up. Buy whole cans; a fraction of a gallon isn’t sold.
Practice workbook
Frequently asked questions
How do I calculate paint needed in Excel?
How much area does a gallon of paint cover?
Should I count primer?
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