Paint Calculator

Enter your wall area to instantly calculate how much paint you need. Accounts for number of coats and coverage rate with this free online paint calculator.

How to Use

  1. Enter wall area

    Input the wall width and height, or enter the total area directly.

  2. Set coating options

    Choose the number of coats and the paint coverage rate (m²/L).

  3. View results

    Click Calculate to see the required amount of paint (L) and estimated cost.

What is paint coverage rate?

The paint coverage rate tells you how much wall area one liter of paint can cover, expressed in m²/L. The higher the coverage, the less paint you need for the same area, which lowers your cost.

Coverage varies a lot by paint type. A typical latex (water-based) paint covers 8–12 m²/L, while primers run around 10–14 m²/L. Rough, absorbent surfaces such as bare concrete or brick reduce the effective coverage.

This calculator finds the total wall area from the room's perimeter and ceiling height, subtracts openings such as windows and doors that you won't paint, and then factors in the number of coats and the coverage rate to estimate how much paint you actually need to buy. Use it for material quotes and budget planning.

Calculation formula

The amount of paint needed is calculated in the following steps.

Gross wall area = 2 × (width + length) × ceiling height
Net wall area = Gross wall area − (windows × 1.5) − (doors × 1.8)
Paint needed (L) = Net wall area × coats ÷ coverage rate

Example: For a room 4 m wide, 3 m long and 2.5 m high painted with 2 coats, the perimeter 14 m × 2.5 m gives a gross wall area of 35 m². Subtracting one window (1.5 m²) and one door (1.8 m²) leaves a net wall area of 31.7 m². At a coverage rate of 10 m²/L, 31.7 × 2 ÷ 10 = about 6.3 L is required.

Frequently Asked Questions

What is paint coverage rate?
Coverage rate is the area one liter of paint can cover (m²/L). Typical latex paint covers about 8–12 m²/L and primer 10–14 m²/L. It depends on the wall condition and paint type, so check the product label.
How much area does one liter of paint cover?
A typical latex paint covers about 8–12 m² per liter. It varies with the wall condition, paint type and dilution ratio, and rough, absorbent surfaces reduce the area covered.
How many coats do I need?
Two coats are generally recommended for an even finish. Going from a light color to a dark one, or painting over a wall in poor condition, may require three or more coats. A primer coat first improves adhesion and color.
How are window and door areas handled?
You subtract the area of windows, doors and other unpainted openings from the total wall area. This calculator assumes a standard window at 1.5 m² and a standard door at 1.8 m², deducting them automatically from the count you enter.
What should I watch out for when estimating paint?
Always subtract the window and door areas, and when buying it is wise to add a 5–10% margin over the calculated result. This allows for touch-up paint and losses during application.
What is the difference between gross and net wall area?
Gross wall area is the full wall surface, the room's perimeter times the ceiling height. Net wall area is what remains after subtracting unpainted openings such as windows and doors, and it is the area actually being painted. Paint quantity is based on the net wall area.
How do I include the ceiling?
This calculator is based on the walls, so calculate the ceiling area (width × length) separately and add enough paint for that extra area. Ceilings usually absorb little, so a coverage rate similar to the walls works fine.
Do I need to calculate primer separately?
For new drywall or a major color change, applying one coat of primer separately is recommended. Primer covers around 10–14 m²/L, more than topcoat, so don't include the primer in the coat count—estimate it separately.
Updated 2026 pricing

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