Room Paint Calculator
Estimate paint for four room walls from length, width, and height. Subtract doors and windows, then account for coats, coverage, and waste.
Height of the walls you plan to paint.
Default interior door opening is about 21 sq ft.
Default medium window opening is about 15 sq ft.
Most interior walls need two coats for even coverage.
Check your paint can label; 350 sq ft per gallon is a common interior estimate.
Adds extra paint for touch-ups, uneven surfaces, and roller tray loss.
- Total wall area
- 352 sq ft
- Adjusted paintable area
- 301 sq ft
- Total coverage required
- 602 sq ft
- Estimated paint needed
- 1.89 gal
- Buying guidance
- Buy 2 gallons
How this estimate is calculated
Estimate = (paintable area − openings) × coats ÷ coverage rate × (1 + waste%). Results update instantly as you edit inputs.
How this estimate is calculated
Estimate = (paintable area − openings) × coats ÷ coverage rate × (1 + waste%). Results update instantly as you edit inputs.
- Total wall area
- 352 sq ft
- Adjusted paintable area
- 301 sq ft
- Estimated paint needed
- 1.89 gal
How to calculate paint needed
Start with the total paintable wall area. In room mode, the calculator uses 2 × (length + width) × height, which covers all four walls without the ceiling.
Subtract doors, windows, or a custom opening area so you do not overbuy for unpainted surfaces.
Multiply the adjusted area by the number of coats, divide by your paint can coverage rate, then add your waste percentage for touch-ups and uneven absorption.
How to subtract doors and windows
Count mode uses editable default opening sizes: about 21 sq ft per standard interior door and 15 sq ft per medium window in imperial units, with metric equivalents provided automatically.
If you measured openings yourself, switch to custom area mode and enter the combined square footage or square meters to subtract.