Paint Calculator
Litres of paint needed by wall area, number of coats, and coverage rate
Frequently Asked Questions
Paint quantity depends on wall area, the number of coats, and coverage rate — and coverage rate is the input people most often get wrong, since it varies by paint brand, surface texture, and surface porosity rather than being a fixed physical constant.
Why the 130 sq ft/litre default is a starting point, not a guarantee
130 sq ft per litre is a commonly cited default coverage rate for standard emulsion paint on a typical interior wall, but actual coverage varies meaningfully by brand and product line, by how porous or textured the wall surface is (a rough or previously-unpainted wall absorbs more paint per square foot than a smooth, previously-painted one), and by application method. The number of coats matters just as directly — a single coat rarely gives even, opaque coverage, especially over a different existing colour, so most jobs budget for two coats minimum, which roughly doubles paint requirement compared to a naive single-coat estimate.
A worked example
The same wall area estimated at the default 130 sq ft/litre coverage versus a paint tin's actual labeled coverage (which might be meaningfully lower for a textured wall or premium thick-coverage product) produces different litre requirements — always check the specific product's tin label for its stated coverage rate rather than relying on a generic default when buying in bulk for a large job, since the gap compounds across the whole area.
How this connects to your other construction planning
Painting is typically the final finishing step after plastering is complete and cured — the wall area used here should match the same plastered wall area from the Plaster Calculator for that room. For a full-house finishing budget across paint, tile, and other final materials together, see the Construction Cost Calculator.
Common mistakes
Assuming the generic 130 sq ft/litre default applies to every paint product, rather than checking the actual tin label for the specific product being used, is the most common source of over- or under-ordering — premium and specialty paints in particular can have meaningfully different coverage rates than standard emulsion.