Grocery Unit Price Calculator
The pack size printed on the price tag or label.
Match the unit type of your pack size — weight, volume, or each — to get a real comparison.
Price per 100g
$1.30
You entered
$6.50 for 500g
$6.50 for 500g works out to $1.30 per 100g — use this figure to compare against other pack sizes or brands on the shelf, regardless of how big each pack is.
Quick answer
A unit price converts a product's total price into a standard measure — like price per 100g or per litre — so you can compare pack sizes and brands fairly, the same way Australian supermarket shelf tags do. Enter a product's price and pack size to see its price per 100g, kg, 100mL, litre or item instantly.
Explore more Everyday calculators
Grocery Unit Price Calculator is one of dates, time and shopping tools on OneCalculate — see the full set for this category.
Browse EverydayHow it works
Unit pricing turns a product’s total price into a price per standard measure — price per 100 grams, per kilogram, per 100 millilitres, or per litre — so you can compare products fairly, no matter how differently their packs are sized. A bigger pack isn’t automatically better value, and a cheaper sticker price doesn’t automatically mean a cheaper product: the only fair comparison is price per unit.
Because unit pricing is genuinely useful for shoppers, Australian consumer rules require large supermarkets to display it directly on the shelf label next to the total price, usually in small print underneath. This calculator does the same maths for any product, so you can check the shelf tag yourself, compare it against a product from a different store, or work it out for something that doesn’t have a printed unit price at all.
The formula behind it is a two-step normalise-then-scale:
1. Convert the pack size to a base unit — grams for weight, millilitres for volume, or a plain count for
items sold individually (kg and L are converted up: 1kg = 1000g, 1L = 1000mL).
2. Divide the total price by that base quantity, then scale the result up to whichever unit you want to
compare against — per 100g, per kg, per 100mL, per litre, or per item.Weight and volume can’t be meaningfully compared with each other — a price per kilogram and a price per litre measure different things unless you also know the product’s density — so this calculator only converts within a matching unit type: weight to weight, volume to volume, or item to item.
Worked example
Marco is choosing between two bags of the same brand of pasta at his local supermarket in Perth: a 500g bag priced at $6.50, and a larger 750g bag priced at $9.00. The bigger bag costs $2.50 more at the register — but is it actually the better buy?
Bag A — 500g for $6.50:
$6.50 ÷ 500g = $0.013 per gram → × 100 = $1.30 per 100g
Bag B — 750g for $9.00:
$9.00 ÷ 750g = $0.012 per gram → × 100 = $1.20 per 100g
Even though Bag B costs $2.50 more up front, it’s actually the cheaper option gram-for-gram — 10 cents less per 100g, which scales up to a full $1.00 less per kilogram ($12.00/kg for Bag B versus $13.00/kg for Bag A). The higher sticker price was hiding the better deal.
| Pack size | Total price | Price per 100g | Price per kg | |
|---|---|---|---|---|
| Bag A | 500g | $6.50 | $1.30 | $13.00 |
| Bag B | 750g | $9.00 | $1.20 | $12.00 |
Bag B is the better buy, even though Bag A has the lower price tag on the shelf — which is exactly the kind of comparison unit pricing exists to make easy.
Frequently asked questions
Why do supermarkets show unit prices?
Australian supermarkets are required to display a unit price — like price per 100g or per litre — next to the shelf price, so shoppers can compare different pack sizes and brands fairly. Without it, a bigger pack with a higher sticker price could actually be the cheaper option per gram, and vice versa.
How do I compare a per-kg price with a per-100g price?
Multiply a per-100g price by 10 to get the per-kg price, or divide a per-kg price by 10 to get the per-100g price — there are always 10 lots of 100g in a kilogram. This calculator does that conversion for you automatically: just pick whichever unit you want to compare against.
Does this work for volumes like milk or juice?
Yes. Select mL or L as your pack size unit and per 100mL or per litre as the unit you want to compare, and the calculator applies the same normalise-then-scale maths used for weight. It works for any liquid grocery item — milk, juice, oil or cleaning products — sold by volume.
Why can't I compare a price per kg with a price per litre?
Weight and volume measure different things, so a price per kilogram and a price per litre aren't directly comparable unless you know the product's density. This calculator blocks that mismatched comparison and shows a hint instead, so you don't end up with a misleading number that looks precise but means nothing.
Is the cheapest total price always the best value?
Not necessarily. A smaller pack with a lower total price can easily cost more per 100g or per litre than a larger pack that looks more expensive on the shelf. Unit pricing exists precisely because sticker price alone is misleading once pack sizes differ — always check the per-unit figure before deciding.
What counts as a 'unit' for things sold individually, like eggs or bread rolls?
For items sold as individual pieces rather than by weight or volume — eggs, bread rolls, toilet rolls — select 'each' as the pack size unit and 'per item' as the target unit. The calculator then simply divides the total price by the number of items, so you can compare cost per item across brands.
Related calculators
Written and verified by Nirbhay Tripathi
Last updated 18 August 2026
All rates on this page are verified againstNSW Fair Trading — Unit pricingon 18 August 2026. See our methodology for the full update calendar.