Paint Calculator

Estimate gallons of paint needed for any number of rooms, accounting for doors, windows, and multiple coats.

Room 1

Length (ft)

Width (ft)

Height (ft)

# Doors

# Windows

Number of Coats

Price per Gallon

How to Use This Calculator

1. Enter room dimensions (length, width, ceiling height) for each room.

2. Enter the number of doors and windows to subtract from wall area.

3. Set number of coats (2 is standard for most projects).

Coverage assumption: 350 sq ft per gallon per coat — typical for quality interior latex. Rough/textured surfaces may need 20% more.

Real-World Examples

12×14 ft room, 8 ft ceiling, 1 door, 2 windows, 2 coats:
Wall area: 2(12+14)×8 = 416 sq ft − 50 = 366 sq ft × 2 = 732 sq ft ÷ 350 = 3 gallons

Open-plan living room 20×30, 10 ft ceiling, 2 doors, 4 windows:
Wall area ≈ 940 sq ft × 2 coats ÷ 350 = 6 gallons

Frequently Asked Questions

How many gallons for a whole house?

A typical 2,000 sq ft, 3-bedroom house with 8-ft ceilings needs roughly 12–15 gallons of interior paint for two coats.

Should I buy gallon or quart cans?

If you need more than 2 quarts of a color, buying gallons is almost always cheaper per ounce.

Do I need primer?

New drywall, drastic color changes, or stain coverage all require primer — roughly the same coverage as paint. Add one primer coat to your calculation.

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