Unit-price comparison
Enter the price, quantity and measurement unit of each pack. The tool converts them to one unit and shows the unit cost of every option, which one is cheapest, and how much more the others cost in percent. It works as a unit price calculator for groceries and bulk buying, so you can see which pack is cheaper at a glance.
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How to use it
- Type a name for each option (optional) and its pack price.
- Enter the pack quantity and pick its unit: g, kg, ml, l, piece and so on. All options must be the same kind of measure: mass, volume, length or count.
- Add options up to six, or remove the ones you do not need.
- Choose the display base (per kg or per 100 g, for example) and read the table: the best value is labelled in text, with the percentage the other options cost on top.
Example
A 500 g pack for 12.00 costs 12 ÷ 0.5 = 24.00 per kg. A 1.2 kg pack for 26.40 costs 26.40 ÷ 1.2 = 22.00 per kg.
The second pack is the best value, and the first is (24 − 22) ÷ 22 × 100 = 9.09% more expensive.
Limits and caveats
- The tool compares price per unit of measure only. It does not consider quality, concentration, shelf life or whether you will use up the larger pack.
- Different kinds of units (grams against millilitres, for example) cannot be compared, because converting between them needs the product density, which the tool does not assume. It explains this instead of showing a result.
- Fluid ounces and gallons are US customary: 1 US fl oz = 29.5735295625 ml and 1 US gal = 3785.411784 ml. Imperial (UK) measures differ and are not supported.
- Ounces (oz) and pounds (lb) are units of mass: 1 oz = 28.349523125 g and 1 lb = 453.59237 g.
- Two to six options. Unit costs are shown with two to four decimals and percentages with two. Two options tie when their unit costs are equal; a difference below one part in a billion is treated as arithmetic noise. The largest accepted price is 1,000,000,000,000.
Questions about this tool
How is the unit cost calculated?
Each pack quantity is converted to one base unit (g, ml, cm or piece), then the price is divided by that quantity and multiplied by the size of the display base you chose. For example, 12.00 for a 500 g pack means 24.00 per kg, or 2.40 per 100 g.
Why does the tool refuse to compare grams with millilitres?
Grams measure mass and millilitres measure volume, and the conversion between them differs for every product (a litre of oil is lighter than a litre of honey). Any number the tool showed would be a guess, so it asks you to use the same kind of unit for all options, as printed on the packs.
What happens when two options cost the same?
When the unit costs are exactly equal, both options are labelled as a tie and the tool does not pick one at random. Decide by the quantity you really need.
How do I calculate the unit price?
Divide the pack price by the number of units in it. A case of 24 bottles for 36.00 is 36 ÷ 24 = 1.50 per bottle. If the quantity is a weight or a volume, convert it to one unit first, such as 500 g = 0.5 kg, then divide.
Is the bigger pack always cheaper?
No, not always, which is why it pays to check the unit price before you buy. A 1 kg pack for 22.00 costs 22.00 per kg, while a 500 g pack for 10.00 costs 20.00 per kg, so the smaller pack is 10% cheaper here. Enter both packs in the tool to see the difference straight away.