Paint Calculator
Work out exactly how much paint you need for any room. Enter your dimensions, the number of coats, and how many doors and windows to subtract.
Paint Calculator
Estimate how much paint you need for a room, including coats and openings.
You'll need about
0 gallons
Enter dimensions to calculate
How to calculate paint
- Measure the length and width of the room, and the wall height.
- Wall area = 2 × (length + width) × height.
- Subtract roughly 20 sq ft per door and 15 sq ft per window.
- Multiply by the number of coats, then divide by paint coverage (about 350 sq ft per gallon).
How much does a gallon of paint cover?
One US gallon of interior paint covers about 350–400 square feet in a single coat. In metric, one liter covers roughly 10 square meters per coat. Most walls need two coats for even color, so plan for double the coverage. Textured or porous surfaces absorb more and reduce coverage.
Frequently asked questions
How much paint do I need for a 12x12 room?
A 12×12 room with 8 ft walls has about 384 sq ft of wall. After subtracting a door and two windows, that's roughly 334 sq ft. With two coats, you'll need about 2 gallons.
Do I really need two coats?
Usually yes. One coat rarely gives even coverage, especially over a different color or fresh drywall. Two coats is the standard for a uniform finish. Use a primer first if covering a dark color.
Does this include the ceiling?
No — this calculates walls only. To include a ceiling, add its area (length × width) to your total separately, since ceilings often use a different paint.