Unit Price Calculator
Use this price per unit comparison calculator to compare packs of different sizes and units and find the cheapest option.
Formula & worked example
Formula: Unit price = price ÷ (size × units per pack × number of packs), converted to a standard unit.
Example: 500 g for 3.00 = 0.60 per 100 g. 1 kg for 5.00 = 0.50 per 100 g, so the larger pack is 20% cheaper.
Method & source: Unit conversion to grams, millilitres or items; SI and US customary factors. See how we test our calculators.
Next step: try percentage change or reverse percentage.
What Is a Unit Price Calculator?
A unit price calculator converts the price of any pack into the cost of a single standard unit, such as per 100 grams, per 100 millilitres or per item. Once every option is priced in the same unit, the best deal is obvious.
This price per unit comparison calculator understands different sizes and measurement systems, so you can compare a 750 g box, a 1.5 kg bag and a 2 lb pack in one go.
How Our Unit Price Calculator Works
Add each product you want to compare with its price, size, unit and number of packs.
- Unit conversion: Grams, kilograms, ounces and pounds; millilitres, litres, fluid ounces and gallons; items and dozens.
- Standard price: Weight and volume are shown per 100 g or 100 ml, counts per item.
- Best value: The cheapest option is highlighted automatically.
- How much more: Every other option shows the percentage extra you would pay.
- Multipacks: Enter the number of packs to compare bundles fairly.
Only like-for-like units can be compared, so the calculator will tell you if you mix weight with volume or count.
Why Comparing Unit Prices Matters
Bigger is not always cheaper. Packaging, promotions and odd sizes make the sticker price a poor guide to value.
- Spot the genuinely cheapest size on the shelf.
- Compare brands sold in different units.
- Check whether a bulk buy really saves money.
- Keep a grocery budget under control.
- Judge promotions such as “3 for 2” objectively.
A quick comparison of price per unit takes seconds and can save a meaningful amount over a year of shopping.
Worked walkthrough: cereal boxes
A 750 g box of cereal costs 3.15 and a 1.2 kg box costs 4.68. Converting both to the same unit gives 0.42 per 100 g for the small box and 0.39 per 100 g for the large one. The larger box is cheaper, and the smaller one costs about 7.7% more per gram. If you add a third option, such as a two-pack of 500 g boxes for 5.50 (0.55 per 100 g), the table ranks all three and marks the best value. Mixed units work too, because pounds, ounces and kilograms are converted to a common base.
Practical tips for unit price calculations
- Only compare like with like: weight with weight, volume with volume, and counts with counts. The tool warns you if you mix them.
- For multipacks, enter the size of one item and the number of packs, for example 330 ml with 6 packs.
- The cheapest unit price is not always the best deal – consider whether you will use everything before it spoils.
- Check promotions: a “3 for 2” offer changes the price you should enter for that pack.
- Shelf labels sometimes use different units for similar products. Enter the pack details yourself to compare fairly.
Frequently Asked Questions (FAQs)
Enter each pack’s price and size, choose the unit and press Calculate. The calculator shows the price per 100 g, 100 ml or item so every pack is on the same scale.
Yes. Weights are converted to a common base, so a 1 kg bag and a 2 lb bag can be compared directly. The same works for litres, millilitres, fluid ounces and gallons.
You cannot compare weight with volume or with item counts. Use the same kind of unit for every product.
Enter the size of a single unit and the number of packs. A 6-pack of 330 ml cans is size 330 ml, packs 6.
Weight and volume are shown per 100 g or 100 ml. Counts are shown per item. The best option is marked and others show how much more you would pay.