🎨 Paint Calculator
Calculate how many litres of paint you need based on room dimensions and number of coats.
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How to Calculate Paint Quantities Accurately
This calculator multiplies the total wall area by the number of coats and divides by the paint's coverage rate (m² per litre). Wall area is calculated as the perimeter of the room times the ceiling height. For a room 5 m × 4 m with 2.5 m ceilings, the perimeter is 18 m, and the wall area is 45 m². At 10 m²/litre with two coats, you need 9 litres — typically rounded up to 10 litres to ensure complete coverage.
Paint coverage varies by product. Economy paints often cover 8–10 m² per litre in a single coat. Premium paints, particularly those marketed as "one-coat" formulations, may cover 12–14 m² per litre and can provide more opaque coverage, potentially reducing the number of coats needed. The tin label always states the manufacturer's coverage rate — use that for the most accurate estimate rather than the default value in this calculator.
Surface preparation significantly affects paint consumption. New plaster, bare wood, or surfaces that have been sanded absorb more paint than previously painted surfaces in good condition. For new plaster, a water-diluted primer coat is usually applied first, which seals the surface and reduces the amount of topcoat paint needed. Skip the primer on new plaster and your topcoat will look patchy, especially with mid-tones and deep colours.
Colour matters for coverage. Deep, saturated colours (dark reds, blues, blacks) require more coats to achieve full coverage than neutral or pastel tones, especially when painting over a contrasting colour. Going from a white wall to a deep navy typically requires 3 coats without a tinted primer, or 2 coats with a grey tinted primer that reduces the contrast. A paint supplier can tint your primer to approximate the topcoat colour and reduce the total amount of topcoat needed.
Buying guide: paint is typically sold in 1 L, 5 L, and 20 L (or metric equivalent) tins. Buying the correct size for your project avoids leftover paint. Store leftover paint upside-down in a tightly sealed tin in a cool, dry place — it will remain usable for 2–5 years for future touch-ups if stored correctly.
How to Calculate Paint Coverage
Paint coverage is calculated by dividing the total wall area to be painted by the coverage per litre stated on the tin. Coverage varies by paint type: standard emulsion covers 10-12 m² per litre on smooth surfaces; textured or porous surfaces may need 30-50% more paint. Always add 10% for waste and touch-ups.
For an accurate estimate: calculate each wall's area (height × width), subtract windows and doors, add a 10% buffer, then divide by your paint's coverage rate. For two coats (recommended for colour changes), double the total.