We tracked the online shelf prices of 630 everyday products at Aldi, Coles and Woolworths for 17 weeks. The answer depends on where you shop, and it has a direct bearing on how much you can trust last week's price.
Every price comparison is a snapshot. A comparison is only as good as the date of its prices, so we wanted to know how quickly a supermarket price goes out of date, and to set our own rules for how old a price can be before we stop using it.
We used the price history behind the OikosAi app: 630 products matched as like-for-like options across the three supermarkets, covering everyday groceries through to cleaning and bathroom products. Over the period we recorded 7,923 weekly price readings.
For both Coles and Woolworths, 70% of prices in our set were exactly the same one week later, which means 30% had moved. At Aldi, 93% were unchanged after a week.
When a Coles or Woolworths price changed within a week, the typical (median) move was about 27–29% of the price. At Aldi, prices changed far less often, and the typical move was about 17%. A move of this size can turn a product from the cheapest option into the most expensive.
At Coles and Woolworths, the share of prices unchanged after four weeks (70% and 73%) was about the same as after one week (70% for both). The pattern points to specials: when a regular price changed within a week, it went down 86% of the time at Coles and 80% at Woolworths. When a special changed, it usually went back up (84% at Coles, 98% at Woolworths).
Of the Woolworths prices marked as a special, only about 1 in 7 was still at the same price a week later. If you see a Woolworths special, the window to use it is usually that week.
62% of the Aldi products we track did not change price at all in any of our readings over the period, compared with 40% at Woolworths and 34% at Coles. Aldi carries no "was / now" special markers, so its list price behaves as a steady everyday price.
Of the 636 store listings in our comparison set, 88 (14%) had not appeared in our weekly collection for more than two weeks. About 3 in 10 of those had simply moved to a new listing at the same store; the rest may have been discontinued, renamed, or not collected.
These results set our own rules. Every price in an OikosAi saving claim:
Because a week-old price at Coles or Woolworths is often out of date, every OikosAi claim shows the dates of the prices behind it.
| Store | Products | Readings | 1wk unchanged | 4wk unchanged | Typical move | Never changed |
|---|---|---|---|---|---|---|
| Aldi | 180 | 2,670 | 93% | 87% | 17% | 62% |
| Coles | 224 | 2,799 | 70% | 70% | 29% | 34% |
| Woolworths | 226 | 2,454 | 70% | 73% | 27% | 40% |
Public online shelf prices collected weekly by OikosAi from the Aldi, Coles and Woolworths websites, 29 May to 27 September 2026 (Aldi from 29 May, Coles and Woolworths from 3 June). One reading per product per collection day.
The 630 products behind the OikosAi comparison set, each matched by hand as a like-for-like option for an everyday grocery or household item across the three stores. This is a curated set of commonly bought items, not each store's full range.
Each price reading was compared with the same product's price about 7 days and about 28 days later. "Unchanged" means the shelf price was exactly the same. The typical move is the median percentage change among prices that changed. Specials are prices the store marked with a higher "was" price.
We see one price per week per store, so a price that changed and changed back between readings is not counted. Prices are online national prices; in-store and regional prices can differ. Multi-buy offers are not captured. Aldi's online prices carry no special markers, so Aldi figures reflect everyday prices only.
About OikosAi. OikosAi is an Australian household savings app that compares everyday grocery prices across Aldi, Coles and Woolworths. We publish this analysis from the same data the app uses, so shoppers can see how our comparisons are built. OikosAi is independent and is not affiliated with or endorsed by Aldi, Coles or Woolworths; their names are trademarks of their respective owners. Prices change often, as this report shows. Always check the current price in store or online before you buy. This report is general information, not financial advice.