Simple Paint Calculator For 2026

What The Paint Calculator Works Out

• Paint needed: wall area x number of coats, divided by the coverage figure, in litres. Standard emulsion covers around 12 m2 per litre per coat (it is printed on every tin); matt often stretches further than silk, and premium or one-coat paints claim more. Most UK living rooms need 5 to 8 litres for walls at two coats, a bedroom 4 to 6.
• 2.5L tins: the litres rounded up to whole 2.5-litre tins, the most common UK size. A typical 4 x 4m room with 2.4m ceilings has roughly 38 m2 of wall, so two coats is a little over six litres and three tins.
• Total coverage: the area that actually gets painted once every coat is counted, which is what the coverage figure on the tin refers to.
• Coats: two is the honest default for a colour change. Buy all the paint for one colour at once and check the batch numbers match, since tint can vary slightly between batches.
• Doors and windows to deduct (advanced): knocks about 2 m2 off per door and 1.5 m2 per average window, so you can enter the gross perimeter x height figure and let the calculator net it down.
• Surface condition (advanced): fresh plaster needs a watered-down mist coat first, which the calculator adds at about 1.5 x the normal coverage because the paint is thinned. Covering a dark colour with a light one usually takes an extra full coat (or a tinted undercoat).
• Tin size and paint cost (advanced): rounds the litres up to whole tins of the size you plan to buy and multiplies by your price per tin. Larger tins are cheaper per litre, so compare a 5L against two 2.5L. The sub-line shows how much is left for touch-ups.
• Time and labour (advanced): assumes about 10 m2 of wall per hour per coat including cutting in. Enter a decorator's day rate (commonly GBP 150 to GBP 250 outside London, more inside) to get a rough labour figure based on whole days.