liminfoPaint Calculator
Free web tool: Paint Calculator
Walls
Total Wall Area
35.0 m²
Net Area
30.2 m²
Paint Needed
6.0 L
Recommended Cans
1 x 4L 3 x 1L
About Paint Calculator
The Paint Calculator helps homeowners, contractors, and interior designers estimate how much paint is needed to cover a room. You input each wall's width and height in meters, specify the number of doors and windows, choose how many coats to apply, and the tool computes the net paintable surface area by subtracting standard door area (0.9 m × 2.1 m per door) and window area (1.2 m × 1.2 m per window) from the total wall area. The result is then divided by a coverage rate of 10 m² per liter to produce the total liters of paint required.
The calculator is particularly useful during renovation planning when you need to budget paint purchases before visiting a hardware store. Rather than buying a single large container that leaves excess waste, it recommends an optimal combination of 18-liter, 4-liter, and 1-liter cans to match the calculated volume with minimal leftover. Multiple walls can be added dynamically for rooms with more than four walls, irregular layouts, or when calculating paint for an entire house section by section.
All calculations run locally in your browser — no data is sent to any server, and no account is required. The tool supports dark mode and is fully responsive for use on mobile devices at the hardware store, helping you make purchasing decisions on the spot. Coverage rates and can sizes are based on typical interior wall paint specifications.
Key Features
- Dynamic wall list — add or remove walls to match any room shape, including L-shaped or multi-sided spaces
- Automatic door deduction: subtracts 0.9 m × 2.1 m per standard door from the gross wall area
- Automatic window deduction: subtracts 1.2 m × 1.2 m per standard window from the gross wall area
- Coat multiplier: choose 1, 2, or 3 coats to match the actual painting plan
- Coverage rate of 10 m² per liter applied to compute total paint volume in liters
- Recommends an optimal can combination using 18L, 4L, and 1L sizes to minimize waste
- Shows gross wall area, net paintable area, and total paint needed side by side for quick review
- 100% client-side calculation — works offline, no sign-up required, dark mode supported
Frequently Asked Questions
How does the paint calculator account for doors and windows?
Each door is assumed to occupy 0.9 m × 2.1 m = 1.89 m² and each window is assumed to occupy 1.2 m × 1.2 m = 1.44 m². These standard dimensions are subtracted from the total gross wall area to give the net paintable area. If your doors or windows are significantly different in size, you can adjust by treating them as additional negative walls.
What coverage rate does the calculator use?
The calculator uses a coverage rate of 10 m² per liter, which is a typical middle-range value for standard interior emulsion paints. High-quality or thick paints may cover 12–15 m² per liter, while cheaper or highly porous surfaces may only achieve 7–8 m²/L. Always check the specific coverage on your paint can label and adjust accordingly.
How many coats should I apply?
Two coats are standard for most repainting work on previously painted surfaces. Three coats may be needed when painting over a dark color with a light one, or when applying paint to bare plaster or drywall for the first time. One coat may suffice for touch-ups or when using a paint-and-primer combined product.
Why are can sizes 18L, 4L, and 1L?
These are the three most common retail paint tin sizes in many markets. The calculator recommends the largest cans first (18L) to minimize the number of containers and reduce cost per liter, then fills the remainder with 4L and 1L cans. This combination minimizes waste while using commercially available sizes.
Can I add more than four walls?
Yes. The "Add Wall" button lets you add as many walls as needed. This is useful for rooms with alcoves, bay windows, or for calculating multiple rooms at once. Each wall has independent width and height inputs, and walls can be removed individually if added by mistake.
Does the calculator include the ceiling?
No, this calculator is designed for walls only. If you also need to paint the ceiling, measure it as an additional rectangular surface and add it as a separate "wall" entry with its own width and height dimensions (length × width of the room).
How accurate is the paint estimate?
The estimate is accurate enough for purchasing guidance but should be treated as an approximation. Actual consumption varies depending on paint brand, wall texture and porosity, application method (roller vs brush vs sprayer), color changes, and painter skill. It is common practice to add a 10–15% buffer to the calculated amount to account for these variables.
What if I am painting over a very dark color?
Painting over a dark color typically requires an extra coat for full coverage. Select 3 coats in the calculator to account for this, or use a tinted primer as the first coat and then calculate 2 topcoats. The tinted primer approach often gives better color accuracy with fewer total coats.