How many gallons of paint per square foot?

One gallon of paint typically covers 350-400 square feet. For two coats, divide your total area by 350, then multiply by 2.

How do I calculate wall area for painting?

Measure each wall's width × height, sum all walls, then subtract door and window areas. A standard door is about 20 sq ft and a window about 15 sq ft.

Paint Calculator

Estimate gallons of paint needed for a room. Enter dimensions, subtract doors and windows.

Room Length (ft)

Room Width (ft)

Wall Height (ft)

Doors

Windows

Coats

Results

Gallons to Buy2 gal

Wall Area352 sq ft

Paintable Area317 sq ft

Exact Needed1.8 gal

How to Use This Calculator

The paint calculator estimates how many gallons of paint are needed for a room. Enter the room dimensions, wall height, number of doors and windows, and the number of coats you plan to apply.

Formula

Wall area = perimeter x wall height. Paintable area = wall area - door area - window area. Gallons needed = paintable area / coverage per gallon x coats.

Example

A 12 ft by 10 ft room with 8 ft walls has 352 sq ft of wall area before subtracting openings. With two coats, it usually needs more than one gallon.

Common Tips

Buy a little extra paint for touch-ups and uneven surfaces.
Primer, dark color changes, and textured walls can increase paint needs.
Always check the coverage listed on the paint can.

Frequently Asked Questions

Related Guides

How to Estimate Paint for a Room

Learn how to calculate paint needed for any room. Covers wall area, coverage per gallon, coats, and common mistakes.