What the comparison includes
Required paint includes your allowance once. Purchased paint rounds up to complete cans. Costs use whole cans and the entered price; cost per finished area uses the net surface, without multiplying it by coats.
Choose per-coat coverage when the label gives m²/L per coat or ft²/US gallon. Choose finished-can coverage when the label already includes all coats. Primer and preparation remain separate.
Worked buying example
For 8 L required, two 5 L cans at €40 each cost €80, with 2 L left over. One 14 L can at €55 costs less but leaves 6 L. These are fictional prices illustrating two different buying objectives.
How can combinations are selected
The search considers every combination that can be optimal for up to four available formats, to a precision of 0.01 volume units and 0.01 currency units. Lowest cost breaks ties by less surplus, then fewer cans. Least surplus breaks ties by lower cost, then fewer cans. Only combine the same product, colour and finish.