Is the bigger package always cheaper per unit?

No. Larger sizes are usually better value but not reliably — promotions, premium packaging, and multipacks regularly invert it. That is exactly what this calculation checks.

Can I compare grams against kilograms?

Yes. Each option keeps the unit printed on its label and everything is converted to a common base before comparing, so a 500 g bag and a 1.5 kg bag are judged on the same scale.

Should I always buy the lowest unit price?

Only if you will use it. Food that spoils, a size that will not fit, or money tied up in stock all cost something the unit price does not capture.

Unit Price Calculator

Work out which package is actually cheaper when the sizes do not match. Enter the price and quantity for each option in whatever units are printed on the label, and every one is converted to the same scale before comparing. The cheapest is marked, and the others show how much more they cost per unit.

Calculators

What the packages are measured in

By weightBy volumeBy count

Name

Price ($)

Quantity

Unit

$6.98 per kg16.5% more than the cheapest

Name

Price ($)

Quantity

Unit

$5.99 per kgBest value

Cheapest per kg: Option B at $5.99.

Sizes are converted before comparing, so a 500 g bag and a 1 kg bag are judged on the same scale. Unit price is only part of the decision — buying more than you use is not a saving.

Private by default

This tool runs entirely in your browser. Your data is never uploaded to a server.

How it works

Putting different pack sizes on one scale

unit price = price ÷ quantity converted to the base unit

Each quantity is converted to a single base — kilograms for weight, liters for volume, or single items for counted goods — and the price is divided by it. Comparing those figures is the whole calculation; the conversion is what makes the comparison honest.

Weight compares against a kilogram, volume against a liter, and counted goods against one item.
Weight and volume are not interchangeable. A recipe asking for 250 ml of something sold by weight needs its density, which no unit price can supply.
Shelf labels in many countries already show a unit price, but the base unit varies between shops and sometimes between products in the same shop.
The percentage shown on each option is how much more it costs per unit than the cheapest one, not a discount.

For reference

A comparison where the big pack loses

Option	Price	Size	Price per kg
Small bag	$3.49	500 g	$6.98
Large bag	$5.99	1 kg	$5.99
Multipack	$9.99	1.5 kg	$6.66
Bulk sack	$21.50	5 kg	$4.30

The 1.5 kg multipack costs 11% more per kilogram than the plain 1 kg bag despite being the larger package — the case unit pricing exists to catch.

How to use

4 clear steps.

Choose whether the products are sold by weight, volume, or count.
Enter each option's price, quantity, and the unit on the label.
Add more options if you are comparing more than two.
Read the price per unit and see which option is marked best value.

Good to know

Frequently asked questions

Is the bigger package always cheaper per unit?: No. Larger sizes are usually better value but not reliably — promotions, premium packaging, and multipacks regularly invert it. That is exactly what this calculation checks.
Can I compare grams against kilograms?: Yes. Each option keeps the unit printed on its label and everything is converted to a common base before comparing, so a 500 g bag and a 1.5 kg bag are judged on the same scale.
Should I always buy the lowest unit price?: Only if you will use it. Food that spoils, a size that will not fit, or money tied up in stock all cost something the unit price does not capture.