Calculate paint and primer quantities for walls, ceiling and trim.
Paint scales linearly with both area and coat count, so the second coat costs exactly as much as the first. Coverage varies with surface porosity, and bare plaster can absorb far more than the quoted figure. Buying in five litre tins rather than litres is substantially cheaper per litre, so rounding up to whole tins is usually the right call.
Paint
Litres = net area × coats ÷ coverage per litre
Litres = net area × coats ÷ coverage per litre Paint scales linearly with both area and coat count, so the second coat costs exactly as much as the first. Coverage varies with surface porosity, and bare plaster can absorb far more than the quoted figure.
Buying in five litre tins rather than litres is substantially cheaper per litre, so rounding up to whole tins is usually the right call.
This calculator takes 5 inputs: Wall area, Openings to deduct, Number of coats, Coverage per litre, Primer required. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.