How to use
Choose weight, liquid volume or item count. Enter each product’s pack price and the total amount covered by that price, then select its unit. The two products can use different compatible units, such as grams and kilograms. Choose a common result unit to compare their rates directly.
For a multipack, enter the combined amount: six 330 mL cans contain 1,980 mL. Enter the number itself rather than an expression. Both prices must be in the same currency and on the same basis, including or excluding any charges consistently.
Calculation method
Each amount converts to a common unit within its measurement family. Unit price = pack price / equivalent amount. The lower unrounded rate determines the cheaper option. Absolute difference = higher rate − lower rate; percentage saving = difference / higher rate × 100.
The comparison uses exact rational values internally. Switching measurement units changes the displayed amount while preserving its underlying quantity. Selecting a new family clears quantities because a mass cannot become a liquid volume without additional information.
Worked example
Product A is 500 g for 3.50. Its rate is 7.00 per kg. Product B is 1 kg for 6.00. B is cheaper by 1.00 per kg, or approximately 14.2857% relative to A’s unit price. Buying B still costs more at the checkout than buying one smaller A pack.
For liquids, 750 mL for 3.00 is 4.00/L. A 1.5 L pack for 5.40 is 3.60/L, which is 10% cheaper per litre.
What the comparison does not establish
The tool does not optimize the number of whole packs to buy. Quality, concentration, edible yield, waste, delivery and tax are not inferred. US and Imperial liquid units remain distinct. It does not convert weight to volume or support dry gallons and troy ounces. A zero pack price is allowed; when both rates are zero, a percentage saving is undefined.
Use the percentage calculator for another relative comparison or the margin calculator when pricing a product for sale.
For the measurement and planning details, read comparing unit prices without confusing pack cost and savings.