How to Compare Unit Prices
Compare differently sized packages without guesswork. Read a concrete example, examine the trade-offs, and try a small exercise to see whether the principle applies to your situation.
Get the key numbers straight
- Start here. Divide total price by a common quantity such as 100 g or one liter.
- Add context. Factor in spoilage and whether you will use the entire package.
- Keep in mind. Beware promotions that change the package size rather than the unit price.
A money example with assumptions
A 750-gram package at $4.50 costs $0.60 per 100 grams, while a 1-kilogram package at $5.80 costs $0.58 per 100 grams. The larger package is slightly cheaper per unit, but only if you will actually use it before spoilage.
The cheapest unit price is only good value when the product is suitable and usable; avoid stockpiling merely for a small headline discount.
Costs, risks and exceptions
Promotional signs can use different measurement units; comparing price per item with price per kilogram misleads. Quantity, quality, waste and transport costs may outweigh tiny savings.
Calculate your own scenario
Write both package quantities in the same unit, divide price by quantity, and compare. For perishables, estimate what portion you will consume.
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Further reading and verification
Read the linked reference for additional background on money & budget. Review the applicable rules and update dates before using any example in a consequential decision.
Scope: Illustrative financial examples only. Taxes, fees, eligibility and product rules vary; this is not personalized financial advice.
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Published October 9, 2026 · BlogJD Editorial Desk · How we prepare and correct content · Report a correction.