Unit Price Comparison — Find the Cheapest Pack

What it is

On a supermarket shelf the sizes differ, so it is hard to see which pack is cheaper. Dividing the price of a 500 g bag, a 1 kg bag, a single item and a 6-pack by hand is tedious. This unit price comparison calculator takes a price, a size, a unit and a pack size for each product, converts everything to a price per 100 g, per 100 ml or per piece, marks the cheapest one and shows how much more expensive the others are. You can compare up to eight products and everything is calculated in your browser.

How to use

1. Enter a name (optional), the price, the size and the unit of each product.
2. For a multipack enter the number of items in the pack size field. Use 1 for a single item.
3. Use the add button for up to eight products. Rows with an empty price and size are ignored.
4. Read the unit price, the cheapest badge and the percentage above the cheapest in the table.
5. Check the formulas below to see how each product was converted.

How it works

• Weight (g, kg) is converted to a price per 100 g, volume (ml, L) per 100 ml and counts per piece.
• Converted size = entered size × unit factor (1,000 for kg and L) × pack size.
• Unit price = price ÷ converted size × base unit (100 or 1).
• The cheapest product is found by multiplying price and size crosswise, so there are no rounding errors.
• Sizes accept up to three decimals and pack sizes are whole numbers from 1 to 10,000.
• Only products of the same kind (weight, volume or count) can be compared.

Example

Product	Price	Size	Price per 100 g	Compared
A	2,500	500 g	500	11.11% above the cheapest
B	4,500	1 kg	450	Cheapest

Comparing a 6-pack of 500 ml at 4,800 with a 2 L bottle at 2,900 gives 160 and 145 per 100 ml, so the 2 L bottle is cheaper.

Common mistakes

Leaving out the pack size and entering only the size of one item makes the unit price several times too high. For a 6-pack, always enter 6 as the pack size. Another common slip is leaving the unit on g while typing a kg value, so check that the unit matches the label on the package. Finally, buying a very large size only because its unit price is lowest can end in waste if you cannot use it all, so consider the expiry date and how you will store it.