Paint Calculator

Manufacturer coverage figures for emulsion run 11–13 m²/litre per coat on a smooth, primed surface. We default to 11 m²/L because real-world coverage usually runs lower than the marketing figure — porous walls, fresh plaster, deep colours, and DIY brushwork all reduce coverage. Always overestimate slightly: running out mid-room is more annoying than buying an extra tin.

Two for most repaints. Three (or two over a primer/undercoat) for: dark colour over light, light colour over dark, fresh plaster, or stained walls. One coat is only realistic for the same colour as before with a high-opacity 'one-coat' product, and even then it usually betrays brush marks.

Because you don't paint them with wall paint. We use typical UK averages (door ~1.85 m², window ~1.4 m²) to deduct from the paintable area. If your doors or windows are unusually large (French doors, full-height glazing), the calculator will under-deduct slightly — round up your tin count by one as insurance.

Already built in by the conservative coverage figure (11 vs the manufacturer's 12–13). For unusual jobs — textured walls, fresh plaster, dark accent walls — add another 10–15% to your purchase. Paint stores well sealed for ~2 years; modest leftover stock is useful for touch-ups.

Almost always — 5 L tins typically save 20–30% per litre vs 2.5 L. The catch is that opened paint deteriorates faster than sealed; if your job needs only 3 L, two 2.5 L tins waste less than one 5 L. Check brand price-per-litre before assuming.

Yes — ceiling-specific paint is matte, low-spatter, and often non-drip. It's possible to use wall emulsion on a ceiling (just thin it slightly) but ceiling paint generally produces a better finish and is no more expensive. This calculator only handles wall area; for ceilings, calculate length × width separately.