Paint Calculator

Buying too little paint means an inconvenient second trip to the store mid-project; buying too much wastes money. This calculator estimates how many liters of paint you need from your wall dimensions, subtracting door and window area, and accounting for multiple coats.

The formula

This calculator assumes a standard coverage rate of 10 m² per liter, a common average for mid-sheen wall paint — check your specific product's label, since coverage varies by paint type and wall texture.

Worked example

A 12 m long, 2.4 m high wall run has a total area of 28.8 m². Subtracting 3 m² for doors and windows leaves 25.8 m² of paintable surface. At 2 coats, that's 51.6 m² of total coverage needed, which at 10 m²/L works out to 5.16 L, rounded up to about 5.5–6 L to leave a margin for touch-ups.

Step-by-step guide

1. Measure the total length of all walls to be painted, and the ceiling height.
2. Multiply length × height to get total wall area.
3. Estimate and subtract the area of doors and windows, which don't need paint.
4. Multiply by the number of coats — two coats is standard for most new colors or significant color changes.
5. Divide by your paint's coverage rate per liter (check the tin) to get total liters needed.

Common mistakes

• Forgetting openings. Skipping the door/window subtraction can overestimate paint needs by 10–15% in a typical room.
• Assuming one coat is enough. Most paint jobs, especially color changes, need two coats for even, opaque coverage.
• Ignoring texture. Textured or porous walls absorb more paint than the standard coverage rate assumes — buy a small buffer extra for these surfaces.

Tips

• Always round up to the nearest full can size available, and keep a little extra for future touch-ups matched to the same batch.

Frequently asked questions