Suppose a four-roll pack costs €5.20 and a six-roll pack costs €7.20. Each inner unit is one roll, so item count is the selected dimension. This comparison assumes rolls are equivalent in sheet count, dimensions, ply, and quality.
Represent multipacks explicitly
One valid entry uses quantity one item and multipack four for the €5.20 option. The other uses quantity one item and multipack six for €7.20. Equivalently, each could use total item quantity with multipack one, but never count both totals simultaneously.
Calculate price per roll
The four-roll option costs €5.20 ÷ 4 = €1.30 per roll. The six-roll option costs €7.20 ÷ 6 = €1.20 per roll. The six-roll pack has the lowest entered unit price, with a displayed saving of €0.10 per roll.
Check whether a roll is a fair unit
Relative to €1.30, the saving is €0.10 ÷ €1.30 × 100 = 7.69%. That number is useful only if the rolls are genuinely comparable. When sheet count or sheet area differs, compare total sheets or area instead of the package’s marketing roll count.