Paint Calculator
Paint calculator helps you calculate the amount and cost of paint needed to paint the walls of a room.
Paint needed1.771 gallons6.71 litres, so buy 2 one-gallon cans
Per coat0.886 gallons
Net area to paint310 sq ft360 sq ft less 50 for openings
Total area painted620 sq ft2 coats
Deducted for openings50 sq ft1 door at 20 sq ft, 2 windows at 15 sq ft
In 5-gallon buckets0.354usually cheaper per gallon above about 4 gallons
Primer, if bare0.886 gallonsone coat over the same area
The method
gallons = area × coats ÷ coverage per gallon
Two coats, and buy whole cans
A gallon covers about 350–400 square feet in one coat on a smooth primed wall. Rough render, bare drywall and dark-to-light changes all drink more, so check the tin — manufacturers state a figure and it is usually optimistic.
Deducting 20 square feet for a door and 15 for a window is the trade convention. It is deliberately conservative: if you plan to paint the trim as well, do not deduct at all.
Buying one extra can is nearly always the right call. Running out mid-wall means a visible lap line, and a second batch may not match exactly.