Unit Price Calculator
Compare 2 to 4 products by price per 100 g, 100 ml or item, see the best value and how much you save against the others.
The formula
Each quantity is converted to a base unit: grams for weight, milliliters for volume, or single items for counts. Unit price = price ÷ quantity in the base unit, and it is shown per 100 g, per 100 ml or per item, with the price per kg or per L beside it. The item with the lowest unit price is the best value.
Saving versus another item = (its unit price − the best unit price) ÷ its unit price × 100. It is how much less you pay per unit by choosing the best item instead of that one.
Conversions used: 1 kg = 1,000 g, 1 oz = 28.349523 g, 1 lb = 453.59237 g, 1 L = 1,000 ml and 1 US fl oz = 29.573530 ml.
Worked example
Item 1 is 500 g for 3.00 and Item 2 is 1 kg for 5.00. Item 1 costs 3.00 ÷ 500 × 100 = 0.60 per 100 g, which is 6.00 per kg. Item 2 costs 5.00 ÷ 1,000 × 100 = 0.50 per 100 g, or 5.00 per kg. Item 2 is the best value, and choosing it saves (0.60 − 0.50) ÷ 0.60 = 16.67% per gram compared with Item 1.
Using it
- Fill in at least two items. Items 3 and 4 are optional, and an item with both price and quantity blank is ignored.
- Each item has its own unit box, so you can compare 500 g against 1 lb or 750 ml against 1.5 L.
- All items must be in the same family: weight (g, kg, oz, lb), volume (ml, L, US fl oz) or count. Mixing them gives an error, because grams cannot be compared with milliliters without knowing the density.
- Results update as you type. Prices are shown without a currency symbol, so any currency works.
- A tie is reported as a tie, and if every item has the same unit price the result says so.
Limits
- It compares price per unit only. Quality, brand, freshness, shelf life, packaging and whether you will use it all are not considered.
- Weight and volume are not converted into each other, since that needs the density of the product.
- A fluid ounce is the US fluid ounce (29.57 ml), not the imperial one. For imperial fluid ounces, enter the volume in ml.
- Prices should be per pack as charged. Multi-buy offers, loyalty discounts, deposits and tax differences must be worked into the price first.
- A pack of several items is entered as the pack price and the total quantity, for example a 6-pack of 330 ml cans as 1,980 ml.
- Unit prices below 1 are shown to four decimals so small differences stay visible; the percentage saving is rounded to two.
Frequently asked questions
What is a unit price?
It is the price of one standard amount of a product, such as 100 g, 1 L or a single item. Dividing each pack's price by its size puts different pack sizes on the same footing so you can see which is cheaper.
Why do I get an error about different families?
You have chosen units that measure different things, such as grams for one item and milliliters for another. The calculator does not convert between weight and volume, so enter all items as weights, all as volumes, or all as counts.
How is the percentage saving worked out?
It is the difference between an item's unit price and the best unit price, divided by that item's unit price. In the worked example Item 1 costs 0.60 and Item 2 costs 0.50 per 100 g, so choosing Item 2 saves 16.67% per gram compared with Item 1.
Is the cheapest unit price always the best buy?
Not always. A larger pack only saves money if you use all of it before it spoils or goes stale, and some stores charge less per unit on a smaller pack on offer. Use the result as one input, not the only one.
How do I compare a multipack?
Enter the pack price and the total quantity. For a 6-pack of 330 ml cans, use a quantity of 1,980 with the ml unit, or use 6 with the count unit if you want the price per can.