How many gallons of paint do I need for a room?
Measure in feet. Typical doors are about 20 sq ft and windows about 15 sq ft.
How this is calculated
Formula: Wall area = 2 × (length + width) × height − 20 per door − 15 per window; gallons = area × coats ÷ coverage.
Assumptions: 350 sq ft per gallon is typical for smooth walls. Textured, porous or new drywall can drop to 250–300; a dark-to-light color change may need a primer coat.
Frequently asked questions
How much does one gallon cover?
Most interior paints cover 350–400 sq ft per coat.
Do I need two coats?
Usually yes for even color, especially over a different color.
Should I buy quarts for small leftovers?
If you need under about 0.25 gallon extra, a quart (¼ gal) is cheaper than another gallon.
Does trim need its own paint?
Trim and doors usually use a semi-gloss and take well under a gallon for one room.