Paint calculator
Calculator
The calculator needs JavaScript. The tables below give the same numbers for common cases.
How it is worked out
- Wall area = perimeter × height = 2 × (14 + 12) × 8 = 416 sq ft.
- Subtract about 20 sq ft per door and 15 sq ft per window: 85 sq ft.
- Gallons = area × coats ÷ coverage = 331 × 2 ÷ 350 = 1.89. Ceilings are not included.
| Inputs | Answer |
|---|---|
| Room length: 14; Room width: 12; Wall height: 8; Doors: 2; Windows: 3; Coats: 2; Coverage of one gallon: 350 | Painting 331 sq ft of wall with 2 coats needs about 1.89 gallons (2 to buy). |
| Room length: 10; Room width: 10; Wall height: 9; Doors: 1; Windows: 1; Coats: 1; Coverage of one gallon: 400 | Painting 325 sq ft of wall with 1 coats needs about 0.81 gallons (1 to buy). |
| Room length: 20; Room width: 15; Wall height: 10; Doors: 3; Windows: 6; Coats: 2; Coverage of one gallon: 350 | Painting 550 sq ft of wall with 2 coats needs about 3.14 gallons (4 to buy). |
How to use it
Wall area is the room perimeter times the height; the calculator subtracts about 20 sq ft per door and 15 sq ft per window and multiplies by the number of coats. Dividing by the coverage of a gallon (check the can; around 350 sq ft is typical) gives the gallons.
Ceilings, trim and heavily textured walls need extra paint. Round up to a whole can and keep a little for touch-ups.
Frequently asked questions
How much paint do I need for a room?
Wall area × coats ÷ coverage per gallon.
How much does a gallon cover?
Check the can; often about 350 sq ft per coat.
Do I paint the ceiling too?
It is not included; calculate its area separately.
Method: standard arithmetic shown step by step; no outside data is used. Checked 2026-11-12.
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General information only. Results are plain arithmetic on the numbers you enter; check anything important (money, health, school work) against your own records or the official source.