Free Paint Coverage Calculator — Gallons for Any Room
Nothing stalls a paint weekend like running out at 80% done — or buying three gallons too many. Enter the room’s length, width, and ceiling height, subtract the doors and windows, choose your coats, and get the gallons to buy, the exact coverage math behind it, and the estimated cost at your paint’s price per gallon. Add the ceiling with one toggle if it is getting a fresh coat too.
Paint Coverage Calculator
Gallons, cost, and a shopping list for any room — calculated from real dimensions, doors, windows, and coats.
1 Your room
2 Paint needed
🎨 Shopping list
How it works
Wall area is perimeter × ceiling height. The tool subtracts standard openings (about 21 sq ft per door, 12 sq ft per window), adds the ceiling area if selected, then divides by 350 sq ft per gallon — the coverage printed on most paint cans — multiplied by your coats. Results round up to whole gallons because stores sell whole gallons, with the exact figure shown so you can judge quart top-ups.
Everyday uses
- Weekend painters — one correct trip to the hardware store.
- Landlords — standardize turnover paint quantities across units.
- Sellers staging a home — budget a whole-house refresh room by room.
- Renters — price an accent wall or single-room refresh accurately.
Frequently asked questions
Why 350 sq ft per gallon?
That is the coverage most manufacturers print for smooth, primed walls. Rough, porous, or unprimed surfaces drink more — plan closer to 300 sq ft per gallon there.
Do I really need two coats?
For color changes and even finishes, yes — one coat rarely covers evenly. Same-color refreshes can get away with one good coat.
Should I buy extra?
A little. Leftover paint from the same batch is the only perfect touch-up match later, so the round-up is a feature, not waste.