Unit price calculator (which is cheaper)
Compare two products by unit price (kg, liter, item) and see which is the better deal.
Use the same unit for both (e.g. grams for A and B).
How the calculation works
Unit price reveals which product is actually cheaper when packs come in different sizes — the supermarket "value" test.
unit price = price ÷ quantity
The product with the lower unit price wins, even if its shelf price is higher.
Step-by-step example
Soap A: R$12 for 1.5 kg. Soap B: R$9 for 1 kg.
- A: 12 ÷ 1.5 = R$8/kg
- B: 9 ÷ 1 = R$9/kg
A costs more on the shelf but is cheaper per kilo.
Use the same unit
To compare, everything must be in the same measure (per kg, per liter, per 100 g). Convert first if needed.
Examples
- Soda 2 L for R$8 vs 600 ml for R$3.50: 4.00/L vs 5.83/L → the 2 L wins.
- Toilet paper: always compare per meter or per equal-length roll.
Frequently asked questions
Is the bigger pack always cheaper?
Not always — that is why you compare the unit price.
Is the bigger pack worth it even if cheaper per unit?
Only if you use it before it expires. Savings that turn into waste are not savings.
Don't many stores already show unit price?
Some do, in small print. But not always in the same unit across brands — worth checking.
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Updated on June 18, 2026 · by Rafael Rossi · Methodology & sources