Use the price for the whole package
Enter the amount you would pay for each option and the quantity included. For a multipack, keep the number of items separate from the amount in each item. A pack of two 500 g bags contains 1 kg in total. Its price belongs to both bags together.
Compare prices in the same currency. If a discount changes what you would actually pay, enter that final package price after checking that you meet the offer’s conditions.
Use “Show unit price per” to choose the unit for the results, or leave it on Automatic. Every option is compared on that same basis.
An example with two sizes of the same food
Imagine a 500 g pack for $3 and a 750 g pack for $4.20. The first costs $0.60 per 100 g; the second costs $0.56 per 100 g. The larger pack has the lower unit price, by about 6.67% relative to the higher unit price.
Now suppose you need just 400 g. The smaller pack covers it for $3, while the larger pack requires $4.20. The two results answer different questions: how much each unit costs, and how much you must spend to buy enough.
Add the quantity you plan to use
The optional needed amount turns a shelf-price comparison into a purchase decision. The calculator works out how many whole packages cover that amount and what each option would leave over. It uses the actual package being sold, including all the inner items of a multipack.
Try changing the quantity to cover another planned dinner. A different package may become more attractive when you have a use for more of its contents. Leave the field empty if you only want to compare unit prices.
Compare like measurements
Weight, volume, and item counts describe different things. A pound and an ounce are compatible weights. A fluid ounce measures volume. The calculator keeps those categories separate, so a 500 g package cannot be compared directly with a 500 mL bottle just because the numbers match.
For a comparison by item, check what one item means. Two boxes with the same number of sachets may contain different amounts in each sachet. Use their net quantities when that is the difference you want to compare.
Let the numbers inform the choice
A lower unit price is useful information, but you also know what fits your cupboard, your recipe, and today’s budget. Review both totals before choosing a larger package. The result does not rate quality, flavor, or whether your household will finish the extra food.
Copy the comparison if you want to keep the options together. Recalculate when a price or package quantity changes; the figures reflect the inputs for this comparison.
The once-a-week grocery shopping guide helps you check that the larger purchase fits the meals and household supplies on this trip.