HisabCalc › Discounts & tips

Unit Price Comparison Calculator

Compares two packs by their true price per unit.

Enter your numbers

Pack A price

Example: 100

Pack A quantity

Example: 2

Pack B price

Example: 180

Pack B quantity

Example: 4

Result

Currency

Figures are computed on your device; nothing is sent anywhere.

Formula

unitA = priceA ÷ qtyA; unitB = priceB ÷ qtyB; cheaper = lower unit; diffPerUnit = |unitA − unitB|

How the calculation works

Dividing each pack's price by its quantity puts both on the same per-unit footing, which is the only basis on which two different pack sizes can be compared fairly.

The cheaper pack is the one with the lower unit price, not the one with the lower sticker price, and the difference per unit tells you how much you save on each unit bought.

The unit is whatever you are buying in, grams or litres or pieces, and it only works if both packs are measured in the same unit.

Common mistakes

Comparing a large pack in grams with a small pack in pieces without converting gives a meaningless unit price.
Assuming the bigger pack is always cheaper per unit: promotions and packaging costs sometimes make the small pack the better buy.

When to use it

Use it in the supermarket aisle when two pack sizes of the same product make it hard to tell which is the better deal.
Do not use it across different products, because unit price only compares like with like.

Worked example

100 for 2 units against 180 for 4 units means B is cheaper by 5 per unit.

Unit price A 50.00

Unit price B 45.00

Cheaper loan B

Difference per unit 5.00

Common questions

What unit should I enter?

Use whatever unit you compare on, such as grams, litres or pieces, as long as both packs use the same one.

Why not just compare pack prices?

A bigger pack usually costs more but can still be cheaper per unit, which is the only fair comparison.

Last updated: 2026-10-04