Paint Calculator
Use this paint calculator to estimate how much paint you need for room walls after subtracting typical doors and windows.
Paint calculator
Adjust the values to estimate material quantity before buying.
Estimated result
Round up for ordering and keep a small project buffer.
- Wall area
- 384 sq ft
- Subtract doors/windows
- 51 sq ft
- Adjusted paint area
- 732.6 sq ft
- Gallons needed
- 2.09 gal
- Cans to buy
- 3 gallon cans
- Estimated paint cost
- $126
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How this estimate works
This calculator turns your project dimensions into a planning quantity, then applies a waste factor so the final number is closer to what you can actually order.
- Wall area = 2 x (length + width) x height
- Paintable area = wall area - door area - window area
- Adjusted area = paintable area x coats x (1 + waste percentage)
- Gallons needed = adjusted area / coverage per gallon
Example
A 12 ft by 12 ft room with 8 ft walls, one door, two windows, and two coats needs about 2 gallons when coverage is 350 sq ft per gallon.
Common planning notes
- Textured walls, deep color changes, and porous surfaces may need extra paint.
- Ceilings, trim, doors, and cabinets should be estimated separately.
- Round up to practical can sizes so you have enough paint for touch-ups.
Frequently asked questions
How much area does one gallon of paint cover?
Many interior paints cover about 350 to 400 square feet per gallon, but the label on your specific paint is the best source.
Should I calculate one coat or two coats?
Use two coats for most repainting projects. One coat may work for similar colors on clean walls with high-quality paint.
Does this calculator include ceiling paint?
No. This calculator estimates wall paint. Calculate the ceiling separately using length times width.