Unit Price Calculator
Compare up to three package sizes to see which is the better value per unit.
Results update as you type.
About this calculator
A unit price calculator divides each item’s price by its size so you can compare different pack sizes fairly and spot the genuinely cheaper deal — the bigger pack is not always the better value. Enter the price and quantity of two products, or add a third under advanced options, in grams, millilitres, sheets, ounces or whatever unit you like (just keep the unit the same across items). It shows the price per unit for each and highlights the best value.
Worked example: a $3.50 pack of 500 g works out to 3.50 ÷ 500 = $0.0070 per gram, while a $5.00 pack of 750 g is 5.00 ÷ 750 = $0.0067 per gram — so the larger pack is about 5% cheaper per gram and is marked as the best value. A comparison table shows each item’s unit price and how much more the others cost.
Shoppers use it to cut through confusing supermarket pricing, compare a multi-buy against a single, and decide whether a bulk size is really worth it.
Frequently asked questions
How do I compare prices with different sizes?
Divide each price by its size to get the price per unit (per gram, per sheet, per millilitre), then compare those figures. A £3.50 pack of 500 g is £0.0070/g while a £5.00 pack of 750 g is £0.0067/g, so the larger pack is slightly cheaper per gram.
Can I compare three products at once?
Yes — open advanced options and fill in Item C. Any item left with a price of zero is ignored, so the tool compares just the two or three you actually enter and marks the cheapest per unit.
Is the bigger pack always cheaper per unit?
Not always. Bulk sizes usually cost less per unit, but promotions, multi-buys and premium large packs can flip that. Comparing the actual unit prices is the only reliable way to tell.
Do the two items have to use the same unit?
Yes — enter both sizes in the same measure (both in grams, or both in sheets, or both in millilitres). The calculator divides price by size directly, so mixing grams for one and ounces for the other would give a meaningless comparison. Convert to a common unit first if the packs are labelled differently.
How do I work out the price per 100 g or per litre?
Enter the size in the base unit and read the per-unit price, then multiply: a per-gram price times 100 is the price per 100 g, and a per-millilitre price times 1000 is the price per litre. Shelf labels usually standardise this way so you can compare against them.
Is the cheapest unit price always the best buy?
It is the best value per unit, but not always the smartest purchase — a huge cheap pack is no bargain if the food spoils before you use it, or if you cannot store it. Weigh the unit price against how much you will actually use.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/unit-price/curl
curl "https://calculator.free/api/v1/unit-price/?price_a=3.5&qty_a=500&price_b=5.0&qty_b=750"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/unit-price/?" + new URLSearchParams({
"price_a": "3.5",
"qty_a": "500",
"price_b": "5.0",
"qty_b": "750"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.