Paint calculator

Get the number of gallons for any room in seconds, with doors and windows deducted and coats included.

Paint Calculator

Length (ft)

Width (ft)

Height (ft)

Number of Coats

Coverage (sq ft/gal)

Cost per Gallon ($)

Total Wall Area:384 sq ft

Gallons Needed:2 gal

Estimated Cost:$90.00

* Calculation assumes standard deduction for doors and windows.

How it works

Wall area = perimeter × wall height.
Subtract about 20 sq ft per door and 15 sq ft per window.
Divide by coverage (about 350–400 sq ft per gallon) and multiply by the number of coats.

Example: A 12 × 12 ft room with 8 ft walls, one door and two windows needs about 1.6 gallons for two coats — buy 2 gallons.

About 350–400 sq ft per coat on smooth, primed walls; less on textured or bare surfaces.

Usually yes — especially when changing colour or painting over new plaster.