How to use
- For each product, enter the price, the size and its unit (g, kg, oz, lb, mL, L, fl oz or items).
- For a multipack, enter the size of one item and the pack count, such as 6 × 330 mL.
- Add products C and D if you want to compare more.
- The best value is named in words, with how much more the others cost per unit.
Unit price formula
unit price = price ÷ quantity
- Both products are converted to the same unit first, so 500 g can be compared with 1 kg, or ounces with pounds.
- Prices from 1 upward are shown to the cent; smaller unit prices get one extra decimal, as US shelf-label rules (NIST Handbook 130) allow.
Examples
3.49 for 500 g vs 5.99 for 1 kg:
- 500 g: 3.49 ÷ 0.5 kg = 6.98 per kg
- 1 kg: 5.99 per kg, the best value
- The bigger bag is 14.2% cheaper per kg; the small one costs 16.5% more.
6 × 330 mL for 4.50 vs 2 L for 2.10: the pack is 1.98 L, so 2.27 per litre, while the bottle is 1.05 per litre.
Handy conversions
| Unit | Equals |
|---|---|
| 1 oz | 28.35 g |
| 1 lb | 16 oz or 453.59 g |
| 1 kg | 35.27 oz |
| 1 US fl oz | 29.57 mL |
| 1 L | 33.81 US fl oz |
Need other units? Try the weight converter.
Tips for comparing prices
- Bigger is not always cheaper. Shops sometimes price large packs higher per unit, and offers on small packs can beat them.
- Compare like with like: weight with weight, volume with volume. Liquids sold by weight need the label’s weight.
- Only buy what you will use. A cheaper unit price is no saving if food goes to waste.
To see what a discount is worth, use the percentage calculator.