Formula
Paintable area = wall area − openings + optional ceiling. Product required = area × coats ÷ coverage, plus the selected allowance.
DIY & HOME PROJECTS
Paint Calculator
Estimate primer and finish paint for walls and ceilings after subtracting openings.
CALCULATOR GUIDE
How to use the Paint Calculator
Estimate wall and optional ceiling paint after accounting for doors, windows, primer, finish coats and each product’s coverage.
Worked example
A net 800 sq ft area with two finish coats requires 1,600 sq ft of coverage, or 4 gallons at 400 sq ft per gallon.
Assumptions and limits
Coverage changes with colour, texture, porosity and application. Trim and cabinetry are not included. Use the coverage printed on the selected product.
Frequently asked questions
How many coats should I plan for?
Two finish coats are typical. A large colour change or porous surface may also need primer.
Does one gallon always cover 400 square feet?
No. Use the coverage printed on your product; rough or porous surfaces normally cover less.
How this calculator works
Enter your known values and select Calculate result. Review units and inputs before relying on the planning estimate.
Actual quantities, prices and requirements can vary. Confirm critical work with a supplier or qualified professional.