Paint Calculator

Find out how much paint you need for a room. Enter the dimensions, number of coats, and how many doors and windows to subtract, and get the gallons and cans required.

Paint calculator

Room length (ft) Room width (ft) Wall height (ft)

Coats Doors Windows Coverage (ft²/gal)

Covers the four walls. Assumes ~350 ft² per gallon per coat, a door ≈ 21 ft², and a window ≈ 15 ft². Buy a little extra for touch-ups.

How to use it

1. Enter the room length, width, and wall height in feet.
2. Set the number of coats and how many doors and windows to subtract.
3. Adjust the coverage if your paint's label differs from ~350 ft²/gallon.

Frequently asked questions

How much paint do I need for a room?

Measure the wall area (perimeter × height), subtract doors and windows, multiply by the number of coats, then divide by the coverage (about 350 ft² per gallon). The calculator does this for you.

How many gallons of paint per coat?

One gallon typically covers 350–400 ft² in a single coat. A standard 12 × 10 ft room with 8 ft walls needs roughly one gallon per coat.

Does the calculator include the ceiling?

No — it covers the four walls. Add the ceiling area (length × width) separately if you are painting it too.