Set up a useful comparison
Use one quantity unit for both packs: grams with grams, litres with litres, or item count with item count. Do not compare the total weight of one pack with the drained weight of another. A lower unit price is useful only if the quantity will actually be used.
Worked example
For a pack costing 12 for 750 grams, one gram costs 0.016. A pack costing 18 for 1,200 grams costs 0.015 per gram. The second pack has a 6.25% lower unit price, even though its total price is higher.
Make the result your own
Replace the example figures, then change one assumption at a time. Read the breakdown as well as the headline answer. The calculator shows its formula and lets you copy or share the result. Shared scenario links include the inputs you choose.
No default is a current market price or an official rate. Calculations do not account for costs or physical effects that are not represented by an input. Check the underlying bill, contract or equipment specification before making a consequential decision.