Bigger isn't always better: Larger sizes and multipack groceries can work out more expensive

BUYING IN BULK is assumed by many consumers to work out cheaper – but a survey of supermarket prices by The Journal has identified 10 products for which a larger pack cost more per equivalent unit than a smaller version.

The comparisons, recorded this week in Tesco, Dunnes Stores, SuperValu and Aldi, covered products including shampoo, laundry detergent, tea bags and chicken.

It’s a legal requirement for supermarkets to display unit pricing – such as the price per 100g – but when a confusing combination of different product sizes and multi-buy or supermarket loyalty scheme offers is at play, smaller sizes can work out cheaper.

But while some differences we found were driven by temporary promotions on smaller packs, others existed at standard prices. 

Taken together, a hypothetical basket containing the larger options for the 10 products in question would cost €93.11.

Pricing exactly the same quantities at the smaller packs’ unit rates would come to €74.58: a difference of €18.53, or 25%.

Calculations

“Internally, you think that if you’re buying more, that you’re going to get cheaper,” said Damien O’Reilly, a lecturer in retail management at TU Dublin.

“If [the smaller size] is on sale, then the multipacks become dearer.”

In general, larger packs can offer savings. But comparing them takes time, particularly when different sizes, special offers and loyalty prices are competing for your attention.

O’Reilly said shoppers can skip those calculations “because it takes too much time and it’s too much mental effort to do it”.

The outliers

Prices are changed fairly regularly at supermarkets, but the biggest percentage gap in our check this week was on Kenco Millicano Americano coffee at Dunnes Stores.

A 90g tin was reduced to €6, while a 140g tin was not on offer and cost €16.15.

That made the larger tin about 73% dearer per kilogram. Two smaller tins would cost €12 and provide 180g of coffee: 40g more than the larger tin, for €4.15 less.

The smaller tin’s promotion is listed as running until 23 November.

One example of a product where the larger size was more expensive per kilogram than the smaller with no special offers at play was chicken in Aldi.

The German supermarket’s 1.9kg Butchers Selection whole chicken, at €6.19, was about 4.5% dearer per kilogram than its 1.6kg version at €4.99, despite both being ‘fresh class A’.

In Tesco, Heinz Original ketchup cost €2.99 for 342g and €4.60 for 460g at standard prices, a premium of about 14% per kilogram for the larger bottle. Neither product had a special offer.

Also in Tesco, a 22-pack of Pampers New Baby size 1 nappies cost €3.60, compared with €16.50 for an 80-pack. At those standard prices, the larger pack was about 26% dearer per nappy.

Four smaller packs would provide 88 nappies for €14.40, eight more nappies for €2.10 less.

To add to the confusion, there is actually a sale on the 80-pack – three for €30 (with a Tesco Clubcard), proving how complex the maths can be to figure out the best value.

The same principle applied to care products. At Dunnes, a 300ml bottle of Aussie Mighty Mega shampoo was half-price at €4. The 400ml version cost €10, or two for €14.

Giving the larger bottles the benefit of that multi-buy still left them 31% dearer per millilitre than the smaller bottle. Both offers are listed as ending on 24 November.

SuperValu’s Hellmann’s Real mayonnaise was €3.50 for 400g on an offer available without membership, compared with €5.99 for 600g, also a gap of about 14% per kilogram.

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At Dunnes, Bewley’s Gold Blend tea was €3.25 for 80 bags, against €7.89 for 160. Lyons Original Blend was €3 for 80 bags on promotion and €7 for 160. The larger boxes were about 21% and 17% dearer per bag respectively.

Persil Bio liquid detergent cost €8 for 35 washes and €14 for 53 washes at standard prices, making the larger bottle about 16% dearer per wash.

Dunnes’ Fage Total 0% yoghurt was €3.50 for 450g and €7.79 for 950g, leaving the larger tub about 5% dearer per kilogram.

It’s worth noting that the overall saving calculated of €18.53 across these products is an illustrative comparison of equal quantities from the smaller packs, rather than a saving you could necessarily make at the till.

It involves fractions of some packs, and the products come from four different retailers. Simply adding up one small pack and one large pack would not give a fair comparison of value – but proves that you’re getting less bang for your buck with some bigger buys.

Why does it happen?

O’Reilly says promotions on individual products can temporarily reverse the savings shoppers might expect from a multipack.

Those offers can be agreed between retailers and suppliers in advance, while different pack sizes may have been bought under different contracts. This is also likely the reason for many of the examples we found being brand items, rather than the supermarkets’ own versions.

“Sometimes the supermarket may have an excess of product and reduce the price on it,” O’Reilly added.

Convenience plays a part too. Comparing different sizes means spending time checking quantities and prices, something shoppers may skip “because it takes too much time and it’s too much mental effort to do it”.

Instead, he said, shoppers can settle on a price they are comfortable paying: “I’m happy with paying five euros, and it takes the pain of having to go and check the prices individually to see what they are, because it does take a bit of time.”

The pattern has been documented beyond Ireland.

In a 2024 analysis, the UK’s Competition and Markets Authority found that although bigger packs usually had lower unit prices, exceptions included toilet roll, cheese and laundry detergent pods.

It also found that a promotion did not invariably make a product cheaper per unit than other sizes sold without a discount.

Asked about our Irish supermarket findings, Tesco spokesperson also referenced promotions having an impact. 

“We work hard to offer customers great value across our range. Products and different pack sizes are priced individually, and prices can also be affected by promotions running at a particular time, meaning a larger pack will not necessarily always have a lower unit price,” the spokesperson said.

“To help customers compare products and choose the option that offers the best value for them, we display unit pricing alongside the selling price, including online.”

Dunnes Stores, Lidl, Aldi and SuperValu were also asked for comment.

How to figure out the best value

The most useful number, then, may be the smaller one on the shelf label: the price per kilogram, litre or item.

For many groceries sold by weight or volume, retailers must display both the selling price and the unit price, such as the cost per kilogram or litre, in shops and online. There are exemptions, but the information helps shoppers compare different pack sizes without having to do all the maths themselves.

For products such as nappies, comparing the cost of each nappy can be more useful than comparing the prices of the bags. With detergent, check the number of washes and the recommended dose as well as the bottle size.

O’Reilly also cautioned against assuming the same offers apply everywhere: “You might get different offers in store than you do online at times.”

And remember: even a cheaper price per kilogram is no saving if the extra food ends up in the bin.

The Environmental Protection Agency estimates that food waste costs the average Irish household about €700 a year.