Home, energy & building
Paint Calculator
Buy the right amount of paint the first time. Enter the room size and wall height, the number of doors and windows, coats and coverage per gallon. The calculator shows gallons and quarts to buy, primer and cost.
How to use the Paint Calculator
- Enter room length, width and wall height.
- Enter the number of doors and windows.
- Choose the number of coats and whether to paint the ceiling.
- Check the coverage on your paint can.
Formula
Wall area = 2 × (length + width) × height - doors × 21 - windows × 15
Gallons = area × coats ÷ coverage
Example
A 14 × 12 ft room with 8 ft walls, 1 door and 2 windows has 365 sq ft of wall. Two coats need about 2.1 gallons - buy 2 gallons and 1 quart.
Tips
- One gallon covers about 350-400 sq ft
- Dark colours over light walls may need 3 coats or a tinted primer
- Buy all the paint for one room at once to keep the colour consistent
Related free tools
Frequently asked questions
Do I need primer?
On new drywall, stains, glossy surfaces or big colour changes.
How much for a ceiling?
Ceilings are length × width; flat ceiling paint covers a little less.
Gallons to quarts?
1 gallon = 4 quarts.
Trim and doors?
Trim uses much less; a quart often does a whole room.
Results are estimates for planning. Your inputs stay in your browser and are not sent to Soft2Cloud.
Last updated: November 2026