Wall Paint Calculator
Enter wall area, cutouts and coverage – get the exact liter requirement instantly
Calculated in your browser – your inputs are not transmitted and are kept on this device only if you choose
Input
Number of coats
2 coats are standard – for good opacity and an even finish.
Paint coverage10 m² per litre
Printed on the paint can (m² per litre and coat).
Paint needed
8litres
8For 40 m² of usable area and 2 coats you need 8 litres of paint (at 10 m² per litre).
- Total wall area
- 40 m²
- Usable area
- 40 m²
How this was calculated
What you can do
Plan a 10–15% reserve
Buy a little more paint than calculated – for touch-ups and leftovers in the can.
RZ-26 · headon.pro
Calculating wall paint correctly: formulas and practical tips
Buying too much is expensive, buying too little forces a reorder – often from a different batch
The formula for paint consumption is simple: liters needed = (wall area − cutouts) × coats ÷ coverage. For a room with 40 m² of wall area, two coats and a paint with 10 m²/L coverage, that works out to 8 liters. Sounds simple – but in practice, mistakes creep in when estimating cutouts and when transferring the coverage value from the label to the real surface.
Coverage in practice: The manufacturer value only applies to smooth, non-absorbent surfaces at a wet film thickness of 100–150 µm. On woodchip wallpaper, fresh plaster, aerated concrete walls or drywall, actual coverage can be 20–40% below the lab value. As a rule of thumb: professionals work with 8–10 m²/L for standard emulsion paint on normal interior walls, and 5–7 m²/L for rough textured surfaces. Always plan a small reserve and buy about 10–15% more than calculated.
Doors and windows as cutouts: A standard interior door (0.90 m × 2.10 m) has an area of 1.89 m². A living room window (1.25 m × 1.40 m) accounts for 1.75 m². In a room with two doors and three windows, cutouts quickly add up to 8–10 m² – at 10 m²/L, that's nearly a liter less paint needed. Precise calculation is especially worthwhile with expensive designer paints.
Watch the batch number: Always buy enough paint from a single production batch (batch number on the can). Paint mixes can vary minimally – not visible on the bucket, but clearly visible on the wall side by side. If a can is missing for the ceiling coat three months later and a new batch has to be bought, color differences are possible.
Typical coverage values by paint category
Coverage of different wall paints
- Basic emulsion: 5–8 m²/L
- Budget renovation paint; for ceilings and less-exposed walls
- Standard wall paint: 8–10 m²/L
- The most common category at hardware stores; sufficient for normal living spaces
- Premium latex paint: 10–14 m²/L
- For damp rooms and heavily used surfaces; washable
- Lime paint: 4–6 m²/L
- Absorbent, breathable; ideal for older buildings and allergy sufferers
- Silicate paint: 6–9 m²/L
- For mineral substrates; durable and mold-resistant
- Facade paint: 6–10 m²/L
- Weatherproof and UV-stable; for exteriors, usually needs 2 coats
Calculation examples
- Wall area
- 40.00 m²
- − Cutouts
- 0.00 m²
- Usable area
- 40.00 m²
- × 2 coats ÷ 10 m²/L
- = 8.00 L
- Wall area
- 25.00 m²
- − Cutouts (windows, doors)
- 4.00 m²
- Usable area
- 21.00 m²
- × 2 coats ÷ 8 m²/L
- = 5.25 L
Frequently asked questions about the wall paint calculator
Everything about paint quantity, coverage and coats
How much wall paint do I need per m²?
It depends on the paint's coverage. Budget wall paints often cover only 5–8 m² per liter, while high-quality emulsion paints achieve 10–14 m² per liter with a single coat. For an even paint finish, two coats are usually recommended. The first coat is the base coat, the second the finishing coat for a clean result. Multiply the wall area by the number of coats and divide by the paint's coverage.
What are cutouts when painting?
Cutouts are areas that are not painted: primarily windows, doors and built-in cabinets. A standard door has an area of about 1.9 m² (0.9 m × 2.1 m), a standard window about 1.5 m² (1.0 m × 1.5 m). These areas are subtracted from the total wall area, since no paint is needed there. Our calculator subtracts the cutouts automatically.
How do I calculate the wall area?
Measure all the walls in the room and calculate the area: width × height for each wall. Add up all the individual areas. Room height in German apartments is usually between 2.40 m (new build) and 2.70 m (older building). For a rectangular room: wall area = 2 × (length + width) × height. Then subtract the areas for doors and windows as cutouts.
Why are two coats standard?
A single coat rarely covers perfectly – especially when the wall paint differs from the existing color, or the wall has absorbed a lot of it (fresh plaster, drywall). The first coat penetrates the wall and seals the pores. The second coat provides the final opacity and an even result. When changing from a dark to a light color, even three coats may be necessary.
What does coverage mean and where do I find the value?
Coverage indicates how many m² a liter of paint covers with one coat. The value is printed on the paint can, usually as "approx. X m²/L" or "coverage at a film thickness of X µm". Budget standard paints: 5–8 m²/L. Mid-range quality: 8–10 m²/L. High-quality premium paints: 10–14 m²/L. On rough or absorbent surfaces, actual coverage is usually 20–30% below the stated value.