Unit price comparison calculator
The bigger pack is not always cheaper per unit. Shelf labels are inconsistent about which unit they use.
Better value option
2
- Option A per kilogram
- 6.4000
- Option B per kilogram
- 6.0000
- How much cheaper the better one is
- 6.25 %
- Difference per kilogram
- 0.4000
- What option B would cost at A rate
- 5.76
Show the working
- Price of option A = 3.2
- Size of option A = 500
- Price of option B = 5.4
- Size of option B = 900
- Option A per kilogram = 3.2 / 500 * 1000 = 6.4
- Option B per kilogram = 5.4 / 900 * 1000 = 6
- Better value option = 6.4 <= 6 ? 1 : 2 = 2
- How much cheaper the better one is = max(6.4, 6) > 0 ? (1 - min(6.4, 6)/max(6.4, 6)) * 100 : 0 = 6.25
- Difference per kilogram = abs(6.4 - 6) = 0.4
- What option B would cost at A rate = 6.4 * 900 / 1000 = 5.76
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- unit price = price / size
Switch the size unit to litres, millilitres or ounces and the comparison still works; both sides use the same unit.