Methodology
GroceryWise compares grocery prices across Coles, Woolworths, Aldi and Chemist Warehouse. This page explains exactly where our data comes from, how we decide two products are the same product, how the price per 100g or litre is worked out, and what we do and don't do with any of it.
How we source data
We run one data importer per retailer (Coles, Woolworths, Aldi and Chemist Warehouse). For Coles, Woolworths and Aldi that means each retailer's publicly published weekly catalogue, read early Wednesday morning AEST — the standard window for new weekly catalogues to go live in Australia. Aldi publishes its Special Buys drops ahead of the day they land, so that one Wednesday read picks up both the Wednesday and the Saturday drop, each dated with its own start and end. Chemist Warehouse has no weekly catalogue and no fixed changeover day; we read its own sale and clearance pages once a week, and show the dates of the campaign catalogues it does publish.
Each importer writes directly to our database. The website reads from the same database, so what you see on a retailer page is what the retailer is publicly advertising for that catalogue window.
How we compare across retailers
A comparison only means something if the two products really are the same product. We group each retailer's items into a single product using several independent identity checks, applied strongest-evidence first, and we record how much confidence each match carries. That grouping is deliberately size-agnostic — a 150g jar and a 400g jar of the same coffee belong together — which is why every row on a comparison shows its own pack size.
Matches made by automated rules that we have not been able to verify are held out of the comparison rather than shown with a caveat. Where we cannot prove two items are the same, we would rather show you less.
How unit prices work
Every unit price on the site is calculated by us, from the pack size, on one measure per product. We do not carry the retailers' own “per 100g” figures across, because they are not always counting the same thing: on the same 12-roll pack of toilet paper one retailer publishes a price per sheet and another a price per roll. Ranking those against each other compares numbers that were never in the same units.
Where a retailer does publish a unit price and it agrees with ours, we credit it to them. Where they publish none, or theirs is on a different measure, ours is marked est.on the page. A calculated figure is never presented as the retailer's own.
Some products cannot be compared per unit at all, and we say so instead of guessing. Multi-buy offers (“2 for $8”) carry a condition rather than a unit price, because the shelf unit price describes the single-unit price and not the deal. Items counted by the piece are compared only when the retailers are counting the same thing — a 12-pack of razor blades against an 8-pack is a comparison, a pack of blades against a razor handle is not. Where we cannot tell, the comparison shows the prices and omits the best-value verdict.
Because pack sizes differ, the best value per 100g is often not the cheapest item on the shelf. Where those differ, we name both.
Where two or more retailers land on the same unit price — which happens on roughly a third of products, because the major chains price against each other — we name all of them. Picking one would read as a reason to shop there rather than the tie it actually is.
What GroceryWise does not do
- We do not manually curate, re-rank, or hand-pick specials. Every product visible on a retailer page came directly from that retailer's catalogue.
- We do not give personal recommendations. There is no account, no shopping history, no profile-based suggestions.
- We do not rank products by affiliate payout. Outbound product links pass through GroceryWise so we can count the click, then go straight to the retailer's own page — no commission in the chain today, and the ranking would not change if there were one.
Pricing accuracy
All prices are in Australian Dollars (AUD), sourced from the retailer's published catalogue. Catalogue prices can change at any time, and in-store pricing can differ from the published catalogue. Always verify the price with the retailer before purchase.
If you spot a comparison that looks wrong — two products grouped that are not the same item, or a unit price that does not match the shelf — please tell us. Getting a comparison wrong is the failure mode we care most about, and we would rather pull a product than leave a misleading number up.
Update cadence per retailer
- Coles: weekly, Wednesday morning AEST.
- Woolworths: weekly, Wednesday morning AEST.
- Aldi:weekly, Wednesday morning AEST — covering the weekly Super Savers and both the Wednesday and Saturday Special Buys drops.
- Chemist Warehouse:we read it weekly, Thursday morning AEST. That is our schedule, not a Chemist Warehouse changeover — it publishes no weekly catalogue, so its prices can change on any day.
Corrections and contact
Spotted a price that looks wrong, or a special that should be on the site but isn't? Drop a note in the GroceryWise Facebook community and we'll take a look on the next refresh.