How this calc works

A gallon of paint covers roughly 350-400 square feet in one coat on a smooth surface — that is the number this calc works from. Give it your wall area and it returns gallons for the coats you are doing. Two coats is the honest default for color changes and new drywall.

The way a painter thinks about it: measure the wall area, do not subtract small windows and doors (the cutting-in around them eats the paint you would have saved), and round up to whole gallons because a gallon you mix yourself never matches the can. The leftover is your touch-up supply.

Common mistakes

The big one is skipping primer on new drywall or a dark-to-light change and then needing a third and fourth coat of finish paint to cover. Primer is cheaper than finish coat; price it in and your gallon count of the expensive paint drops.

The second is trusting "one-coat" marketing. One-coat coverage assumes a similar existing color and perfect application. For any real color change, plan two coats and buy accordingly.

RELATED FORMULAS