Paint Calculator — Wall Paint Required in Litres

Calculate paint required for walls including doors, windows and number of coats.

About this calculator

A paint calculator estimates how many litres of paint you need to cover a wall, room, or exterior surface — based on the area, the coverage per litre of your specific paint, and how many coats you plan to apply. Buying too little means an emergency mid-job trip to the shop and a potentially mismatched batch; buying too much wastes money on expensive emulsion that will dry out before you use it again.

Most water-based interior emulsions cover 12–14 m² per litre per coat on a smooth primed surface. Textured or porous surfaces (rough plaster, bare brick, raw wood) consume significantly more — sometimes only 6–8 m² per litre. Always check the manufacturer's coverage spec on the can rather than relying on a generic number.

Formula

L = \frac{A \times c}{C}

  • A — Total surface area to paint (m²)
  • c — Number of coats (typically 2)
  • C — Coverage per litre (m²/L per coat)

Worked example

Inputs: Living room: walls 4 × 4 m, ceiling height 3 m · 2 coats · Paint coverage: 13 m²/L

  1. Wall area = 4 walls × (4 m × 3 m) = 48 m²
  2. Subtract doors/windows: estimate 6 m² → net 42 m²
  3. For 2 coats: total surface = 42 × 2 = 84 m²
  4. Litres needed = 84 ÷ 13 = 6.5 L → buy 7 L (one 4 L and one 4 L, keep extra for touch-ups)

Frequently asked questions

How much paint for an exterior?

Exteriors typically need 10–15% more paint than interiors because of texture, exposure, and absorption. Also factor in primer separately — masonry primer covers about 10 m²/L. For a typical 200 m² Indian villa exterior with 2 coats of emulsion + 1 coat primer, plan for 35–45 L of paint and 20 L of primer.

Should I tint paint myself or have the shop do it?

For colours other than pure white, always have the paint shop machine-tint with the manufacturer's tint system. Hand-tinting risks colour batch inconsistency — even a 1% tint variation between cans is visible on a finished wall. Order all paint for one room at the same time so it comes from a single batch.

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