Paint Calculator
Use this paint calculator to estimate how much paint you need for a room or interior project. Enter the room dimensions, door and window openings, number of coats, and paint coverage so you can buy the right amount the first time. It also estimates cost when you know the paint price per liter.
Result
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What This Paint Calculator Helps You Do
Use this paint calculator to estimate how much paint you need for a room or interior project. Enter the room dimensions, door and window openings, number of coats, and paint coverage so you can buy the right amount the first time. It also estimates cost when you know the paint price per liter.
How to Calculate Paint Calculator
- Measure the room - Enter the room length, width, and wall height to get the wall area.
- Add doors and windows - Include opening dimensions and counts so the calculator can subtract the painted area that will not be covered.
- Choose coats and coverage - Set the number of coats and the paint coverage from the can label or supplier sheet.
- Check paint and cost - Review the final liters and total cost before you place the order.
Paint Calculator Formula
| Symbol | Definition | Unit |
|---|---|---|
| L | Room length | m |
| W | Room width | m |
| H | Room height | m |
| C | Coats | count |
| E | Coverage | m2/L |
Worked Examples
- length: 5
- width: 4
- height: 2.6
- doors: 1
- doorWidth: 0.9
- doorHeight: 2.1
- windows: 2
- windowWidth: 1.2
- windowHeight: 1.2
- coats: 2
- efficiency: 10
Result: Paint needed = 8.41 L
This is a practical room-painting estimate with openings removed from the wall area. The estimate is 8.41 L.
- length: 4.5
- width: 3.5
- height: 2.4
- doors: 1
- doorWidth: 0.9
- doorHeight: 2.1
- windows: 1
- windowWidth: 1.0
- windowHeight: 1.1
- coats: 1
- efficiency: 11
Result: Paint area = 35.41 m2
Area gives you the substrate size before you multiply by coats and coverage. The estimate is 35.41 m2.
- length: 6
- width: 4
- height: 2.7
- doors: 1
- doorWidth: 0.9
- doorHeight: 2.1
- windows: 3
- windowWidth: 1.1
- windowHeight: 1.1
- coats: 2
- efficiency: 9
- pricePerLiter: 11
Result: Paint cost = 118.51 $
The cost result helps when you compare paint brands with different coverage rates. The estimate is 118.51 $.
- length: 8
- width: 6
- height: 3
- doors: 2
- doorWidth: 1
- doorHeight: 2.1
- windows: 4
- windowWidth: 1.5
- windowHeight: 1.2
- coats: 2
- efficiency: 8.5
Result: Paint needed = 17.08 L
Larger rooms benefit from the same area calculation before paint is purchased. The estimate is 17.08 L.
How to Interpret Your Results
| Range | Meaning | Action |
|---|---|---|
| < 2 L | Very small job | Usually enough for a patch or touch-up area. |
| 2–10 L | Small room | Typical for a bedroom, office, or accent wall. |
| 10–30 L | Medium room | Common for living rooms, kitchens, and larger spaces. |
| > 30 L | Large project | Check product coverage carefully and buy a little extra for safety. |
Frequently Asked Questions
Sources
Last reviewed: March 2026