Wall Paint Calculator
Estimate paint from a known wall area. Subtract openings, then account for the number of coats, label coverage, and waste allowance.
Enter the total wall area if you already know it.
Use this when you know the combined opening area.
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
- 40 sq m
- Adjusted paintable area
- 36 sq m
- Total coverage required
- 72 sq m
- Estimated paint needed
- 9.21 L
- Buying guidance
- Estimate 9.3 L — buy 10 liters
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
- 40 sq m
- Adjusted paintable area
- 36 sq m
- Estimated paint needed
- 9.21 L
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.
Paint coverage assumptions and why rates vary
Most interior latex paints list coverage around 350–400 square feet per gallon on smooth, primed drywall. Rough or porous surfaces, dark color changes, and spraying often need a lower coverage assumption.
This tool keeps coverage editable so you can match the label on the can you plan to buy. When in doubt, use the lower number on the label to avoid a mid-project store run.