PROJECT ESTIMATOR / 01

Paint
Calculator

Estimate paint for all four walls of a rectangular room, including doors, windows, and multiple coats.

Room length (ft)

Room width (ft)

Wall height (ft)

Doors to subtract (20 sq ft each)

Windows to subtract (15 sq ft each)

Number of coats

Coverage per gallon (sq ft)

Planning note: Coverage varies by product, surface texture, color change, and application method. Always check the paint label before buying.

How the estimate works

We calculate the perimeter of the room, multiply it by wall height, subtract 20 square feet for each door and 15 square feet for each window, then multiply by the number of coats. The result is divided by your paint’s coverage and rounded up to a whole gallon.

A gallon typically covers about 350–400 square feet. This calculator starts at 400, but the product label should take priority.

Method checked against guidance from Sherwin-Williams and Benjamin Moore.