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Feeling unsure about nappy sizes? You’re not alone!
Tiny newborn nappies look impossibly small… until suddenly they don’t. One minute you’re folding down the top to fit that squishy little tummy, the next you’re dealing with mystery leaks and wondering if it’s time to go up a size.
At Kids Planet, we partner with Kit & Kin to use gentle, eco-friendly nappies in our nurseries wherever we can, and our team change a lot of nappies every day. We know that confusing weight bands, growth spurts and wiggly babies can make nappy sizing feel like guesswork.
The good news is that there are clear signs to look out for. Here’s how to tell when to size up your child’s nappy, plus answers to the questions we hear most from parents.
Every brand has slightly different size bands, and they often overlap. That’s helpful in theory, but in real life it can leave you staring at the packet thinking, “3 or 4… which are you?!” Rather than focusing only on the number on the pack, look for these five signs:
If you’re suddenly changing more outfits (and cot sheets) than nappies, it could be time to size up. Smaller nappies hold less, so as your little one grows, they may out-pee the absorbency. If the nappy feels very heavy or saturated after naps or overnight, or your baby wakes with a red or irritated bottom, it might be struggling to keep up.
With Kit & Kin nappies, the next size up offers more absorbency and a better fit around the legs. At nursery, our colleagues will keep an eye on leaks and let you know if they spot a pattern.
Gently check your baby’s skin when you change them. If you’re noticing red marks around the waistband or leg cuffs, or it looks like the nappy is digging in, it’s likely too tight.
You might also spot a bit of sweat around the waistband, especially in warmer weather or after an active play session outdoors. That’s another sign that the nappy is on the snug side.
💡 Soothing tip: Sizing up usually makes a big difference to comfort. If your baby’s skin is already a bit sore, Kit & Kin’s Magic Salve can be a lovely option for chapped or irritated areas.
Sometimes you can simply see that a nappy isn’t quite right. A good fit should be:
You want a softer, looser feel at the front and back so there’s space for movement, rolling, crawling and all that wonderful exploration we love to see in nursery – from loose parts play indoors to Udeskole-inspired learning outside. 🌿 If you’re constantly adjusting the nappy to get it to sit right, it may be time to move up a size.
When you fasten the nappy, the tabs should meet somewhere near the centre of the waistband. If you’re tugging to get them to reach, or they’re sitting close to the edges, that’s your sign. As soon as you can’t fasten the tabs easily without pulling or “wiggling” the nappy into place, it’s worth trying the next size up.
Crawling, cruising, walking, climbing onto everything in sight… once your child gets moving, quick changes become your new superpower. This is often when parents choose to switch to pull up nappy pants. Nappy pants can be especially helpful if:
Kit & Kin eco nappy pants start at size 4 and go up to size 8, and they can be a great stepping stone towards potty training.
If your little one is near the top of the weight range for their current nappies and at the lower end of the next size, moving up is usually a good idea. A slightly bigger nappy is often more comfortable and more absorbent than a too snug one.
If you’re a Kit & Kin nappy subscriber at home, you can exchange unopened packs if you realise your baby has raced ahead to the next size – helpful for those growth spurts that seem to happen overnight.
Look at the overall fit and comfort. It’s time to try the next size up if:
The “two-finger rule” is your friend. Once the nappy is on:
If your fingers fit comfortably, the nappy is tight enough to prevent gaps, but not so tight that it’s digging in.
Somewhere in the middle.
Aim for a snug fit below the belly button, with the leg cuffs sitting nicely in the crease at the top of the thighs.
Yes, ideally the tabs should close somewhere near the centre of the nappy front.
If you’re having to really tug the tabs, or they’re landing close to the very edges, try the next size up. A better fit at the waist usually means fewer leaks during naps, outdoor play and car journeys.
For most standard nappies, no. The waistband should sit just below the belly button, not over it.
There should still be enough room to slide two fingers between the waistband and your baby’s skin so they can move, stretch and play comfortably.
Many parents like to have Size 1 nappies ready to go. If you’re using Kit & Kin, Size 1 suits babies from 2–5kg (around 4–11lbs).
If you’re expecting a smaller or premature baby, consider size 0 or smaller newborn nappies. Your midwife or health visitor can help advise on this too.
For most babies, yes. Kit & Kin size 1 nappies are designed for 2–5kg (4–11lbs), and the average newborn falls well within this range.
In early weeks, you may fold the waistband slightly or adjust tabs to get a snug fit. Your baby may move into size 2 quite quickly as they feed more often.
There’s no exact timeline. As a guide, Kit & Kin size 1 nappies often last from birth to around two months.
Move up sooner if you notice leaks, red marks or the other signs we’ve mentioned. Our colleagues at Kids Planet are always happy to chat if you’re unsure.
There’s a lot of variation at this age. On average, many 12-month-olds are in around size 4 nappies, but there are no hard and fast rules. Use the signs: Any red marks? Frequent leaks? Tabs no longer meeting?
By 12 months, most children are crawling or walking, so it might be a good time to try pull up nappy pants for quicker changes. At Kids Planet, we support toilet learning in partnership with you, taking your child’s unique needs and any SEND support into account so the process feels calm and positive.
Nappy sizing, toilet learning, sleep, nutrition, big feelings – early parenthood brings a lot of questions. At Kids Planet, we’re here to make life a little easier.
Our early years educators use their knowledge, experience and strong parent partnerships to spot when nappies might need sizing up, support children’s independence and keep them comfortable through every messy, magical stage.
If you’d like to know more about how we use Kit & Kin nappies in our nurseries, or how we support your baby’s early years education and care – from funded childcare options to child-led learning and Udeskole-inspired adventures – we’d love to chat.
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