How Much Paint Do You Need? Room-by-Room Guide
One gallon covers 350-400 sq ft. Here is the math for every room in your house.
Wall area = room perimeter times ceiling height, minus doors (21 sq ft each) and windows (15 sq ft each). Most rooms need 2 coats. Divide total coverage needed by 350 to get gallons. A 12x12 room with 8-foot ceilings: perimeter 48 ft times 8 = 384 sq ft, minus 1 door and 2 windows = 333 sq ft. At 2 coats: 666 sq ft / 350 = 1.9 gallons. Buy 2 gallons.
Cost by Room
Bedroom: 2 gallons ($60-80). Living room: 2-3 gallons ($60-120). Kitchen: 1-2 gallons ($30-60). Bathroom: 1 gallon ($30-40). Whole house interior: 10-15 gallons ($300-600). Professional painting adds $2-6 per square foot of wall area for labor.