What is in this guide
To compare unit prices before buying household basics, put similar products on the same measurement basis, then compare the cost for that amount. Before choosing the lower figure, check that the product suits the job, the full pack fits your spending limit and you can use what you buy.
1. Match the product before comparing the number
Start with one item already on your shopping list. Put two acceptable options side by side, whether they are different brands or different pack sizes of the same product.
Decide what must stay the same. For bin liners, that might be capacity and fit. For handwash, it might be a formulation your household already accepts. A cheap pack that fails your basic requirements does not belong in the comparison.
Keep this separate from planning the whole trolley. Feeding a family on a weekly grocery budget covers that broader task; this method answers the narrower question of which acceptable pack costs less for a matching quantity.
2. Read the measurement beside the price
The ACCC describes unit pricing as the cost of a standard amount, which lets you compare similar products across different packs. Find that measurement beside the selling price and read it in full: per litre, per 100 mL, per kilogram, per item or another stated unit.
Do not compare the figures until the units match. A price per 100 mL and a price per litre describe different quantities, even when both bottles contain the same type of liquid.
To convert a price per 100 mL to a price per litre, multiply it by ten. The same conversion takes a price per 100 g to a price per kilogram. Keep both prices in dollars, or both in cents, throughout the calculation.
If the units already match, no conversion is needed. Compare the displayed unit prices, then check the total amount payable for each pack.
3. Calculate it yourself when the label is missing
Some retailers or products may not have displayed unit prices, as the ACCC’s coverage guidance explains. Use the pack’s stated contents and its current selling price to calculate your own.
Unit price = pack price divided by pack quantity, multiplied by the comparison quantity.
Choose the formula that matches what is printed on the pack:
| What you want to compare | Calculation |
|---|---|
| Price per 100 mL | Pack price ÷ total millilitres × 100 |
| Price per litre | Pack price ÷ total litres |
| Price per 100 sheets | Pack price ÷ total sheets × 100 |
| Price per bag or tablet | Pack price ÷ total number of bags or tablets |
For a multipack, include all the contents. Multiply the number of identical containers by the quantity in each before dividing the price. For toilet paper, multiply rolls by sheets per roll if a total sheet count is not supplied.
Keep the unrounded calculator result until the end. Write the chosen unit next to your answer so it remains meaningful when you compare another pack later.
4. Check what the unit price leaves out
Toilet paper: the ACCC identifies price per 100 sheets as the comparison unit. Use that to compare quantity, then consider ply and sheet size separately. A sheet count alone does not establish that two products will feel or perform alike. Avoid judging value by the number of rolls without checking their contents.
Laundry detergent: when comparing different concentrations, add a cost-per-wash calculation. Use the pack quantity and the labelled dose for the same washing conditions: pack quantity divided by dose gives the calculated number of washes; pack price divided by that number gives cost per wash. Keep quantity and dose in matching units. If the instructions do not provide comparable doses, leave this comparison unresolved rather than guessing. It does not establish cleaning performance.
Bin liners and dishwasher tablets: a per-item figure is useful only after checking that each option suits the intended bin or appliance. Treat compatibility as a requirement before comparing cost.
Refills: check whether you already have the compatible dispenser. If you need to buy one, include it in the initial purchase decision rather than judging the first purchase on refill cost alone.
5. Recheck specials and larger packs
For a multi-buy offer, divide the total promotional price by the total quantity you must buy to receive it. Compare that result with the single pack you would otherwise choose. Use an offer only if you meet its stated conditions.
Then ask where the extra stock will go and when you expect to use it. Check the cupboard before buying more. A lower unit price is a quantity advantage; it does not remove the need to pay for the whole pack today.
If the larger pack crowds out something needed this week, choose the affordable amount. A family budget that survives a real month provides the wider framework for deciding how much is available for household purchases.
For an online order, inspect the final basket as well as the product listing. Include any delivery charge or other fee in the decision about where to place the order, rather than assuming a lower item unit price guarantees a lower total.
6. Make one useful comparison note
On your next shop, choose one household basic and compare two acceptable packs. Record the product description, pack quantity, current pack price, matching unit price, shop and date. Add any condition needed for that price, such as buying multiple packs.
Circle the option you can afford, store and use. Keep the note for your next purchase, but recheck the price and contents then. The useful record is a comparison you can update, not a permanent declaration that one pack is always better value.
How we checked this: Checked against ACCC unit-pricing guidance on 19 September 2026. The calculations and shopping checks are editorial guidance; no products were tested and no current retail prices or savings are claimed.
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