Same product, different sizes
Pack A: $6.50 for 750 g = $0.87 per 100 g. Pack B: $4.40 for 450 g = $0.98 per 100 g. Pack A is cheaper by about 11 cents per 100 g, even though its shelf price is higher.
Compare two grocery pack prices and quantities on the same basis: per 100 g, 100 mL or item. See which pack costs less and by how much.
Unit Price Calculator Australia
Compare two pack prices per 100 g, per 100 mL or per item. Enter weight in grams or kilograms and volume in millilitres or litres; the calculator standardises the comparison units.
Which pack is actually cheaper?
The pack with the lower unit price is cheaper for the same amount. Compare like with like—such as dollars per 100 g or per litre—not the shelf price alone. A larger pack or advertised special can still cost more per unit.
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How this unit price calculator works
Enter each pack’s price, quantity and unit. Weight inputs in grams or kilograms are shown per 100 g; millilitre or litre inputs are shown per 100 mL; count inputs are shown per item. There is no output-unit selector.
Formula
For weight: price ÷ grams × 100. For volume: price ÷ millilitres × 100. For count: price ÷ number of items. Convert kilograms to grams or litres to millilitres before applying the relevant formula.
Comparing two packs
- Use the checkout price for the quantity you will actually buy.
- Enter the same measurement type for both packs: weight with weight, volume with volume, or count with count.
- Check the lower standardised unit price, then consider usable contents, waste and storage.
Compare two supermarket packs
Compare mixed pack units
A 1 kg pack at $8.50 costs $0.85 per 100 g; a 600 g pack at $5.70 costs $0.95 per 100 g. The calculator standardises kilograms and grams before comparing.
For a meaningful comparison, both packs must use the same type of quantity: weight with weight, volume with volume, or items with items. It cannot compare 500 g against 500 mL because that would require product density.
Common mistakes
These are the mistakes that make a simple calculator result less useful than it should be.
- Comparing price per kg with price per 100 g without converting.
- Assuming bigger packs are always cheaper.
- Ignoring waste if you cannot use the larger pack before it spoils.
- Letting sale labels distract from the actual unit price.
Limits of a unit-price comparison
The result compares price per measured amount. It does not account for differences in concentration, quality, edible yield, waste, delivery costs or how much of the pack you will use. Compare like products using the same unit and check the current shelf or checkout price.
Unit conventions and rounding
Convert both pack sizes to the same mass, volume or item basis before comparing. For example, $6.50 for 750 g is $0.8667 per 100 g; show $0.87 after calculating. Keep the unrounded value when comparing two close prices.
Mass and volume cannot be compared without knowing the product’s density. A price per 100 g and a price per 100 mL are different measures.
The ACCC’s unit-pricing guidance explains standard grocery comparison units. This tool is a shopping comparison, and does not determine retailer compliance with the unit-pricing rules.
When unit price alone misleads
Suppose a 1 kg bag costs $8 and a 600 g bag costs $5.40. Unit prices are $0.80 and $0.90 per 100 g, so the larger bag wins if you use it all. If 300 g of the larger bag spoils, its effective cost rises to roughly $1.14 per 100 g of food actually used ($8 ÷ 700 g × 100).
In another example, a “two for $6” offer on 300 g packs costs $1.00 per 100 g. A single 750 g pack for $6.50 is cheaper at about $0.87 per 100 g. Sale signage is not a substitute for calculating.
Use unit price with the real pack and serving size
Compare prices only after converting both products to the same unit. Grams must be compared with grams, millilitres with millilitres and item counts with item counts. A sale badge, larger pack or multi-buy offer is not automatically cheaper per unit.
When the cheapest unit price is not the cheapest decision
A lower unit price can still waste money when the pack expires, storage is limited, quality differs or the household will not use the full quantity. Compare the usable amount, not only the advertised pack size.
For regulated trade measurement or disputed shelf labels, keep the receipt and product details and check the current Australian consumer or trade-measurement guidance rather than relying on this calculator alone.
Unit Price Calculator FAQs
What is unit pricing?
Unit pricing shows the cost in a standard unit, such as price per kilogram, per litre, per 100 grams or per item. It is useful when two products have different pack sizes or one is on special.
Why use per 100 g instead of per kg?
Small packaged foods are often easier to compare per 100 g. The correct unit is the one used consistently across the products being compared.
Does the cheapest unit price always win?
No. Waste, quality, storage, cash flow and whether you will actually use the product still matter.
Which calculator should I use next?
After using the Unit Price Calculator, use the related calculator links on this page to check the next most relevant number instead of relying on one isolated result.
Bottom line
Use the same comparison unit for both packs. A lower price per 100 g, 100 mL or item means better value per measured amount, but only if the contents are comparable and you will use what you buy. Check the actual shelf price, product quality, storage and expiry before choosing a bulk pack.
Reviewed for calculator quality: This finance calculator was checked for input clarity, formula notes, rounding behaviour, examples, related links and general-information limitations. See the methodology notes and editorial review profile.