Why the coverage figure on a UK paint tin rarely matches reality

Most tins claim up to 17 m²/L, but that number is measured on a smooth, primed test panel. On bare new plaster or plasterboard, trade emulsion from Dulux Trade or Crown Trade typically covers closer to 12-13 m²/L because the surface is porous and soaks up the first coat. New plaster also needs a diluted "mist coat" before the proper coats, which uses extra paint that this calculator's coat count should include.

VAT on DIY paint in the UK

Paint bought for a DIY project carries standard-rate VAT at 20%, with no reduced rate available. That is different from some building work carried out by a VAT-registered tradesperson on certain qualifying renovations, where a reduced 5% rate can apply to labour and materials together. Buying the paint yourself and hiring a painter separately does not qualify for the reduced rate.