Measure walls, not floor space
For rectangular rooms, wall area starts with perimeter × height. Subtract openings only where appropriate and add ceilings if they are being painted. Treat woodwork separately if it uses a different paint.
Coverage is a product specification
Use the coverage stated on the tin and adjust for the surface. Bare or porous areas, strong colour changes and defects can require priming or additional coats. The result gives litres before rounding to available tin sizes.
Preparation is real work
Ask whether filling, sanding, stain blocking, protection and clearing the room are included. A low paint bill says little about the time needed to produce a sound finish.
Common questions
Does this calculate how many tins to buy?
It calculates litres. Round up using the tin sizes you intend to buy, leaving a sensible amount for touch-ups.
Sources & methodology
This page uses original budgeting guidance and transparent arithmetic. Example prices are chosen illustrations, not a survey of UK market prices. Replace them with written quotations.
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