Why do UK nappy prices vary so much between packs, brands and subscriptions?

Why does the pack price not tell me what a nappy costs?

A nappy aisle shows you perhaps thirty prices between £1.70 and £14, and none of them is the number you need. Packs hold anywhere from 22 to 174 nappies. The same brand sells the same size as a 'carry pack', an 'essential pack' and a 'jumbo' or 'jumbo+' pack. Promotions apply to some pack sizes and not others. A subscription adds delivery and a discount for committing. The pack price is an input; the cost of one nappy is the output.

That output is called the unit price. For products sold by number, the Price Marking Order 2004 (as amended in 2024) defines it as the price for an individual item, and the government's guidance gives the example of a four-apple pack at £3 being labelled '£0.75 each'. Nappies are sold by number, so a pack of 48 at £2.85 should carry a shelf label of about 5.9p or '£0.06 each'. Everything else in this guide is that one division, applied carefully.

Cost per nappy is not the same as cost per day. A newborn may need 10 to 12 changes a day according to the NHS; a toddler six to eight. A cheap size 1 nappy used twelve times costs more per day than a dearer size 5 used six times. Compare pence per nappy within a size, then multiply by your own change count.

How much does the same size 4 nappy cost per nappy right now?

We picked size 4 (roughly 9 to 14 kg) because it is the size babies stay in longest and the one every brand sells in several pack formats. The rows below are live listings from two supermarkets' websites and one subscription brand, all fetched on the same day. Tesco, Asda and Boots block automated checks of their product pages, so we could not include them; the method is identical and their sites show the same 'per each' figure.

Three things jump out. The cheapest and dearest nappy of the same size differ by a factor of five. Two supermarkets' own brands landed on exactly the same price for exactly the same pack count, which tells you own-brand nappies are priced against each other rather than against Pampers. And Pampers on promotion was closer to own-brand than to its own shelf price, which is why the question 'is Pampers worth it?' has no fixed answer: it depends entirely on which week you ask.

Why does pack size change the unit price, and are big packs always cheaper?

For own brands, pack size barely matters: Morrisons' 84-pack saved 0.1p a nappy over its 48-pack. Own-brand nappies are already priced near cost, so there is little room for a bulk discount. For branded nappies the picture inverts. The ordinary shelf price of the small 'essential' pack (25p to 30p a nappy) is far above the jumbo pack (16.7p), and the jumbo is in turn undercut by the multibuy (11.9p). Brand pricing is built around pack architecture: the small pack anchors a high price, the big pack looks like a bargain against it, and the multibuy rewards the shopper who commits £20.

But the promotion on the small pack (£6 for 44, 13.6p) beat the jumbo pack's standing price (16.7p) on the day we looked. Which is exactly the point the Competition and Markets Authority makes in its short guide to unit pricing: items on a promotional offer are not necessarily the best value, and neither are the biggest packs. The CMA also notes that the unit price may be printed smaller, and harder to find, when a loyalty or promotional offer is running. You have to read it every time.

• Small pack on promotion wins when the discount is 40% or more and you only need a week's supply.
• Jumbo at standing price wins when there is no promotion on and you have storage.
• Multibuy wins on paper but only if you use both packs in the same size. A baby who moves up a size after one pack has paid 16.7p, not 11.9p.
• Own brand wins almost every week on unit price alone; whether it wins for your baby depends on fit and leaks, which price cannot tell you.

Why is a size 1 nappy cheaper than a size 4, and does that change what I spend?

Bigger nappies use more absorbent core and more elastic, so each one costs more to make, and fewer fit in a pack. Within Aldi's own range the unit price roughly triples from newborn to toddler sizes.

The right-hand column is the useful one. Even though a size 6 nappy costs three times a size 1, the daily spend only roughly doubles, because a toddler is changed half as often. It also explains a common surprise: newborn packs feel expensive because they disappear in two days, not because the nappies are dear. A pack of 24 at 12 changes a day is two days' supply.

There is a second, quieter effect of size on cost: buying too many nappies in a size the baby is about to leave. Babies sit in sizes 1 and 2 for weeks, not months, so buy small packs until you know how fast yours is growing.

How do I read the shelf-edge unit price, and can I trust it?

Under the Price Marking Order, shops must display both the selling price and, where applicable, the unit price. For a product sold by number that unit price is 'each'. On a supermarket shelf edge it is usually in smaller type under the main price, in a form like '£0.06 each' or '5.9p per nappy'; online it sits next to the price as '(5.9p/item)' or similar.

There are three gaps to know about. First, the legislation exempts 'small shops' with a relevant floor area under 280 square metres, so a convenience store need not show a unit price at all. Second, the government's guidance says traders 'should endeavour' to show unit prices on promotional items, price reductions and multi-buys, which is softer than 'must'; in practice many shelf labels show the unit price of the standing price but not of the deal. Third, the CMA's 2024 review of loyalty pricing and its unit-pricing blog both record that unit prices are sometimes missing, inconsistent between products, or simply wrong. When the label is missing or looks odd, do the division yourself: pack price divided by pack count.

Official guidance (Price Marking Order 2004 guidance, GOV.UK) gives the unit price for items sold by number as the price of one item, for example '£0.75 each'. Nappies fall in this category, so a nappy shelf label without a per-nappy figure is one you can query with the store.

When is a nappy subscription cheaper than supermarket packs?

Subscriptions vary the price in a different way: a discount for committing, bundled delivery, and a larger box than any supermarket pack. Pura's size 4 box holds 144 nappies at £41 one-off or £32.80 on subscription, with free next-day delivery in both cases; Kit & Kin advertised 'up to 24%' off for subscribing on the day we checked. The subscription saving is real, but it is measured against the brand's own one-off price, not against the supermarket.

Against the supermarket the arithmetic is unforgiving. At 22.8p a nappy the subscription was nearly four times the own-brand unit price and still above Pampers on promotion. A subscription nappy that is also sold in supermarkets (Pura Soft was 31.3p in a 24-pack at Morrisons) is cheaper direct than on the shelf, so if you have chosen that brand for other reasons, the subscription is the cheaper way to buy it. The value case for subscriptions is therefore about the brand, delivery and not running out, not about beating own-brand on price.

• Check the cancellation window. Pura's terms let you cancel or suspend up to three days before a scheduled delivery; a box that arrives after a size change is dead money.
• Watch box sizes. 144 nappies at 8 changes a day is 18 days; if the baby is near the top of the weight band, order less often.
• Compare delivered cost. Supermarket home delivery slots and minimum spends add to the pack price too; a subscription with free delivery removes that line.

How do I compare a promotion, a multipack and a subscription fairly?

Six lines in a notes app are enough. Do it once per size and you have a personal 'good deal' threshold that no advert can talk you out of.

1. 1
   Fix the size Only compare nappies of the same size number. A size 4 at 6p and a size 5 at 7p are not a 1p difference; they are different products for different babies.
2. 2
   Record pack count and price for each option Write down count, selling price, and whether the price is a standing price, a promotion, a loyalty price or a multibuy. Note the date; supermarket promotions usually run for a fortnight or less.
3. 3
   Divide to get pence per nappy Price in pence divided by count. For a multibuy, divide the total (for example £20) by the total nappies in both packs. Check your answer against the shelf-edge 'each' figure; if they disagree, trust your division.
4. 4
   Add delivery if you are not carrying it home Add the delivery fee or slot cost divided across everything in the basket. A subscription with free delivery is compared at its pence-per-nappy figure directly.
5. 5
   Multiply by your daily change count Use your own count from the last two days, not a brand's estimate, to get a cost per day for each option.
6. 6
   Set a threshold and stop Write your own-brand pence-per-nappy figure at the top of the note. Any branded nappy at or below it is a genuine deal; anything above it is a preference you are paying for, which is fine if you know it.

In shortIn short: UK nappy prices vary because you are shown pack prices, not nappy prices. On the day we checked, the same size 4 nappy ranged from 5.8p (supermarket own brand, big pack) to 31.3p (subscription brand in a supermarket small pack), with Pampers anywhere from 11.9p to 29.7p depending on pack and promotion. Read the 'each' figure on the shelf edge, do the division yourself when it is missing, and judge every deal against your own-brand baseline.