Paint Calculator
Calculate exactly how many gallons or liters of paint you need to buy for any room.
Room Dimensions
Settings
Estimation Results
Total Wall Area0 sq ft
Paintable Area (minus doors/windows)0 sq ft
Paint Needed (2 coats)0 gal
Cans to Buy0 1-gallon cans
For estimation purposes only. Actual coverage depends on surface texture, paint brand, and application method.
How This Calculator Works
The paint estimator calculates total wall surface area, subtracts the standard space taken up by doors and windows, and applies a standard paint coverage rate to give you a precise material estimate.
The formula for paint is: Gallons = (Total Paintable Square Footage × Number of Coats) ÷ 350. (For metric: Liters = (Square Meters × Coats) ÷ 8.6).
Example Calculation
For a 15x20 foot room with 8-foot ceilings, 2 doors, and 3 windows, doing 2 coats:
- Wall Perimeter: 15 + 15 + 20 + 20 = 70 feet
- Gross Wall Area: 70 × 8 = 560 sq ft
- Deductions: 42 (2 doors) + 36 (3 windows) = 78 sq ft
- Net Paintable Area: 560 - 78 = 482 sq ft
- Total Area for 2 Coats: 482 × 2 = 964 sq ft
- Gallons Required: 964 ÷ 350 = 2.75 gallons
- You will need to buy 3 gallons of paint.
Common Room Sizes (2 Coats)
| Room Size | Paintable Area | Paint Required (Gallons) |
|---|---|---|
| 10' × 10' | 275 sq ft | 2 gallons |
| 12' × 12' | 339 sq ft | 2 gallons |
| 15' × 20' | 482 sq ft | 3 gallons |
| 20' × 25' | 642 sq ft | 4 gallons |
Paint FAQs
How much does 1 gallon of paint cover?
One gallon of interior paint typically covers 350 to 400 square feet with one coat. If you are applying two coats (which is recommended for a professional finish), one gallon will cover about 175 to 200 square feet.
How many gallons of paint do I need for a 12x12 room?
For a standard 12x12 room with 8-foot ceilings, you have about 384 square feet of wall space. After deducting a door and two windows, you'll need about 1 gallon of paint for a single coat, or 2 gallons for two coats.
How many square meters does a litre of paint cover?
One litre of standard interior paint generally covers about 8 to 10 square meters with one coat. Two coats will require double the amount of paint.
Do I need to prime the walls first?
You should use a primer if you are painting over a dark color with a light color, painting new drywall, or painting over a glossy finish. Primer covers at roughly the same rate as paint (about 350 sq ft per gallon).
How much paint for the ceiling?
Ceiling paint covers about 350 square feet per gallon. To find your ceiling area, multiply the room's length by its width. A 12x12 room is 144 square feet, so you will only need 1 gallon for the ceiling.