Paint Calculator
Estimate gallons of wall paint from room perimeter, wall height, openings, coats, and paint coverage.
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How this calculator works
Paintable area = perimeter × wall height − openings. Gallons = paintable area × coats ÷ coverage.
Worked example
A 64 ft perimeter room with 9 ft walls, 70 sq ft of openings, and two coats needs about 2.9 gallons at 350 sq ft/gal.
Sources & assumptions
Paintable wall area subtracts entered openings and multiplies by the selected coats. Coverage is visitor-editable because surface texture, color change, application method, and product specifications affect spread rate.
Frequently asked questions
How much area does a gallon of paint cover?
Many interior paints are rated around 350 to 400 sq ft per gallon per coat. Check the specific product label.
Do I need primer?
Primer may be needed for bare surfaces, stain blocking, major color changes, or manufacturer requirements.
Room-by-room paint guide
Use the worked room examples and measurement checklist in How much paint do I need?