Why do size 6 nappies cost more per nappy than size 4 at Tesco, Asda and Aldi?

Why does the ticket pence rise with nappy size?

A size 6 nappy is cut for a heavier child (Which?'s size guide puts size 4 around 7–18kg and size 6 at 16kg+). More absorbent core and a larger chassis cost more to make, and retailers put fewer pieces in the bag so the box still fits the shelf. The selling price of the bag may look similar to a size-4 jumbo; the unit price — the VAT-inclusive price for one item under the Price Marking Order — goes up because you are dividing by a smaller count.

That is a size-step effect, not the same question as why Tesco, Asda and Aldi differ from each other on one size. Store-to-store and brand-to-brand variation is a different comparison. Here the useful check is size 4 versus size 6 in the same shop, same brand, same week.

How much did Which? record on the size ladder in 2024?

Which?'s Aldi versus Lidl table used the highest price of the largest pack for each size between 1 and 30 June 2024. It is the clearest published UK ladder from about 3p to 11p. Treat every cell as June 2024, then re-read Tesco, Asda and Aldi £/each today.

The same Which? nappy guide put disposable pence in a wide band from about 6p to nearly 30p depending on brand, and found own-brand size-4 48-packs clustered near 6.1p across Aldi, Tesco Fred & Flo, Lidl and others for the year to 30 June 2024. Size 6 on that own-brand cluster is the 8p rung above, not a jump to branded carry-pack pence.

Does a higher pence mean a higher weekly spend?

Not by itself. Which? says a young baby often uses six to 12 disposable nappies a day, and that the number falls as they get older. A toddler in size 6 who has four or five changes can spend less in a week than a size-4 baby on eight to ten, even if each size-6 nappy is 2p dearer.

Night-time plus packs and nappy pants have their own £/each. Mixing a size-6 tape pence with a size-6 pant pence, or a 6+ night line, will recreate a 'size is expensive' story that is really a style mix.

How should I read size 6 versus size 6+?

They are neighbouring lines, not two names for one nappy. Which? lists size 6 at 16kg+ and size 6+ at 17kg+, and its June 2024 Aldi/Lidl table jumps from 8p (60-count) to 11p (46-count). Aldi also describes plus sizes as extra absorbency. Tesco's size-6 and 6+ grocery aisle mixes Fred & Flo plus packs and branded carry packs — Tesco.com showed a Pampers Baby-Dry size-6 carry pack of 19 at £5.50 / £0.29 each on 10 September 2026, which is a carry-pack premium on top of the size step.

• Size 6 taped, own-brand jumbo. The fair comparison with size 4 own-brand jumbo in the same shop.
• Size 6+ / extra absorbency. Higher pence, fewer in the bag. Use it only if that is the line you need overnight or for a heavier wee.
• Size 6 branded carry pack. Express-style counts (around 19) show a third, much higher, pence. Do not use that ticket to explain why own-brand size 6 exceeds size 4.

How do I check this week's Tesco, Asda and Aldi tickets?

1. 1
   Pick one brand in one shop Fred & Flo size 4 next to Fred & Flo size 6, or Mamia 4 next to Mamia 6, or Little Angels 4 next to Little Angels 6.
2. 2
   Copy count and £/each for each size If the unit line is missing, divide selling price by the count on the pack. That is the Price Marking Order arithmetic.
3. 3
   Keep 6 and 6+ on separate rows If only 6+ is on the peg, do not call it size-6 pence.
4. 4
   Multiply by this week's changes, not by 10 'because baby' A toddler week and a newborn week are different volumes. The dearer nappy can still be the cheaper week.

In shortIn short: size 6 usually costs more each than size 4 because the nappy is larger and the bag holds fewer pieces. Which?'s June 2024 Aldi/Lidl ladder ran 6p at size 4 and 8p at size 6, then 11p at 6+. Re-read Tesco, Asda and Aldi £/each this week, and convert to a weekly total with the number of changes you actually do.