Unit Price Calculator
Compare packs by their price per kilo, per litre or per piece, and see which is really cheapest and by how much.
Runs entirely in your browser. Nothing is uploaded, logged or stored.
Cheapest for the quantity
Product 2
- Its price per unit
- 4.79 / kg
- Less than the dearest, per unit
- 0.19 / kg
- Cheaper than the dearest by
- 3.8 %
Is the big pack really cheaper? Give the price and the quantity of each pack, and this brings them all to the same unit — per kilo, per litre or per piece — and names the cheapest. Add a product for each pack on the shelf.
How it works
Each price is divided by its quantity in the family's base unit: 500 g at 2.49 is 0.5 kg, so 4.98 a kilo. Centilitres and millilitres become litres, and pounds and ounces become kilos at their exact definitions.
The cheapest is the lowest price per unit; the saving is how much less it costs than the dearest, per unit and as a percentage.
Weights are compared with weights, volumes with volumes and pieces with pieces. A gram and a litre cannot be compared without knowing what is in the pack, so the page refuses rather than guesses.
Examples
| Case | Input | Result |
|---|---|---|
| Three packs of the same thing | 500 g at 2.49, 1 kg at 4.79, 1.5 kg at 7.35 | 4.98, 4.79 and 4.90 a kilo — the 1 kg pack, 3.8 % cheaper |
| Drinks by the litre | 33 cl at 0.85, 1.5 L at 1.95 | 2.58 and 1.30 a litre |
| Sold by the piece | 6 eggs at 2.10, 12 eggs at 3.84 | 0.35 and 0.32 a piece |
Frequently asked questions
How do I work out the price per kilo?
Divide the price by the weight in kilos. 500 g is 0.5 kg, so 500 g at 2.49 is 2.49 ÷ 0.5 = 4.98 a kilo. For a price per litre, do the same with the volume in litres.
Is the bigger pack always cheaper?
No, which is the reason to check. Promotions on small packs and large packs priced for convenience both happen, and the shelf label does not always show the unit price the same way for every pack.
Why can I not compare grams with litres?
Because a litre of oil, of water and of honey do not weigh the same. Converting would need the density of the product, which the page does not know, so it asks you to compare packs measured the same way.
Good to know
- Amounts carry no currency: the answer is in whatever you put in.
- Results use double precision floating point arithmetic. That is exact enough to decide with and is not an accounting record.