Paint Calculator
Use this free paint calculator to figure out exactly how much paint to buy. Enter your room dimensions, subtract doors and windows, choose your number of coats, and get an instant estimate.
How to Use This Calculator
- 1
Measure your room
Enter the room length, width, and wall height in feet.
- 2
Count openings
Enter the number of doors and windows to subtract from the wall area.
- 3
Select options
Choose the number of coats, paint quality, and whether to include the ceiling.
- 4
Get your estimate
See how many gallons you need and estimated costs by paint quality.
Frequently Asked Questions
A 12x12 room with 8-foot ceilings has about 384 sq ft of wall space. After subtracting a door and two windows, you need roughly 2 gallons for two coats with standard coverage paint (350 sq ft/gal).
Most interior paints cover 300–400 sq ft per gallon. Economy paints cover less (~300 sq ft), while premium paints can cover up to 400 sq ft per gallon.
Two coats are recommended for most projects to ensure even coverage, especially when changing colors. One coat may suffice for touch-ups or when using the same color.
Ceilings should be painted if they are stained, discolored, or if you are changing the room color significantly. Use a flat/matte ceiling paint for best results.