What is a paint calculator?
A paint calculator helps you estimate how much paint you need to cover the walls of a room. By entering the room's length, width and height, you get the total wall area and the number of liters of paint required.
How to calculate how much paint you need?
The amount of paint is calculated using the following formulas:
Wall area = 2 × (length + width) × height
Paint needed = wall area × number of coats / coverage rate
The coverage rate is usually printed on the paint can and indicates how many square meters one liter of paint can cover in a single coat.
What is a typical paint coverage rate?
Average paint coverage is about 10–12 m² per liter for one coat, but it varies depending on paint type, surface texture and application method. Priming a rough surface may reduce coverage to 6–8 m² per liter.
Paint calculation examples
Small room: 3 × 3 m, height 2.5 m, 2 coats, coverage 10 m²/L. Wall area = 2 × (3 + 3) × 2.5 = 30 m². Paint needed = 30 × 2 / 10 = 6 L.
Large room: 6 × 5 m, height 2.8 m, 2 coats, coverage 10 m²/L. Wall area = 2 × (6 + 5) × 2.8 = 61.6 m². Paint needed = 61.6 × 2 / 10 = 12.32 L.
When to use a paint calculator?
A paint calculator is useful when planning a renovation or room refresh. It helps you buy the right amount of paint so you do not have to make extra trips to the store or waste money on excess paint.
Tips before painting
- Always buy 5–10% more paint than calculated — some will be used for touch-ups.
- Rougher surfaces (e.g. textured plaster) require more paint.
- Dark colors over a light surface may require 3 or more coats.
- Window and door areas are not subtracted — this serves as a natural buffer.