How to Calculate How Much Paint You Need
Buying the right amount of paint saves money and avoids multiple trips to the paint store. The calculation involves measuring the total wall area, subtracting doors and windows, dividing by the paint's coverage rate (typically 10–14 m² per litre), and multiplying by the number of coats. Always round up to the next full tin.
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Formula
Paint Calculator
Calculate how many litres of paint you need to cover a room or surface.
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Worked Example
Given:
Related Calculators
FAQs
How do I calculate the wall area of a room?
Measure the perimeter of the room (sum of all wall widths) and multiply by the ceiling height. For a 4 m × 5 m room with 2.5 m ceilings: perimeter = 2(4+5) = 18 m, area = 18 × 2.5 = 45 m². Subtract door area (~2 m²) and window areas (~1.5 m² each) for the net paintable area.
How many coats of paint do I need?
Two coats give best coverage and durability for most situations. One coat may suffice for the same colour repaint in good condition. Three coats may be needed for dark colours over light, painting over dark colours, or applying water-based paint over oil-based. Always allow full drying time between coats.
Does paint brand and type affect coverage?
Yes significantly. Premium paints with higher pigment content typically cover 10–14 m² per litre, while budget paints may achieve only 7–9 m². Matte and flat paints generally cover more than gloss finishes. Always check the manufacturer's stated coverage on the tin, as it varies by product.