Unit Price Calculator settles the supermarket-aisle question properly: which package is actually cheaper per unit of product? Enter each option's shelf price, content amount and unit — grams, kilograms, millilitres, litres, ounces, pounds or pieces — and every package is normalised to the same denominator: price per 100 g for weight, per 100 ml for volume, per piece for counted goods. Multipacks multiply the content before dividing, which is where mental arithmetic usually fails. The cheapest option is flagged and every other package shows the percentage premium you would pay for choosing it, which turns "the big one is probably cheaper" into a number — and surprisingly often, it is not.
Features
Price per 100 g, per 100 ml or per piece, chosen automatically
Weight, volume and count units, metric and imperial
Multipack support: 6 × 330 ml is computed as 1,980 ml
Best-value flag on the cheapest package
Premium percentage on every costlier option
Any number of packages compared at once
Refuses to compare weight against volume rather than mislead
Everything computed on your device
How to use the Unit Price Calculator
Enter each option's price, amount and unit
Set the pack count for multipacks
Add more options as needed
Read the unit prices, the best-value flag and the premiums
Example
Input
500 g at $3.49 vs 1.2 kg at $7.99
Output
$0.70 vs $0.67 per 100 g — the big pack wins by 5%
Closer than the shelf makes it look; sometimes the small pack wins.
Common errors & troubleshooting
Two products will not compare. — One is measured by weight and the other by volume — no honest unit price bridges grams and millilitres without a density. Convert one side manually (for water-like liquids 1 ml ≈ 1 g) or compare within one kind.
The multipack looks worse than the singles. — That happens more than supermarkets would like you to believe — check that the pack count is entered, and if it is, believe the result. Bulk formats carry a convenience premium surprisingly often.
Shelf-edge unit labels disagree with the calculator. — Stores print unit prices against different denominators — per kg on one label, per 100 g on the next shelf. The calculator uses one denominator per unit kind precisely so options stay comparable.
The drained weight makes the comparison unfair. — For canned goods in liquid, the drained weight on the label is the honest content figure. Enter that instead of gross weight when comparing against dry alternatives.
Frequently asked questions
What is a unit price and why does it matter?
It is the cost per standard quantity — per 100 g, per litre, per piece — rather than per package. Packages are designed to be hard to compare; unit price is the one number that makes every size and brand directly comparable.
Is the bigger package always cheaper per unit?
No, and that assumption is what stores monetise. Promotions on small sizes, shrinkflation on large ones and multipack convenience premiums regularly invert the expected order — compute rather than assume.
How do I compare a 6-pack against a single large bottle?
Enter the 6-pack as its single-container size with a pack count of 6 and the total pack price. The calculator multiplies content, not price, and puts both options on the same per-100 ml scale.
Why compare per 100 g instead of per kilogram?
They are the same comparison at different scales — per 100 g just keeps supermarket numbers readable, cents rather than fractions of a dollar. European shelf labels use the same convention for the same reason.
When is the cheaper unit price not the better buy?
When the bigger pack expires before you finish it, needs storage you lack, or tempts overconsumption. Unit price measures cost per amount, not value per household — it is the start of the decision, not the whole of it.