Size 4 diaper: up to what age or weight?

In collaboration with Rokiyah Hosen

Relecture professionnelle

Is your baby continuing to grow and you're finding it increasingly difficult to close his size 3 diaper? Are you wondering at what age and weight size 4 corresponds? We explain everything you need to know about this diaper size in this article.

Everything you need to know about size 4 diapers

The size 4 baby diaper is designed for babies weighing between 7 and 18kg. This corresponds to babies from 6 months to around 18 months.

After 6 months, your baby's growth and weight gain slow down. Size 4 diapers are worn longer than previous sizes.

When should I start using size 4 diapers?

As soon as the size 3 diaper diaper becomes too small, you can switch to size 4 diapers. How can you tell if a diaper is too small?

If you can fit two fingers between the diaper and your baby's tummy, size 3 is still suitable for your child. But if you're having trouble, it may be a sign that it's time to switch to the next size up, and that the size 3 diaper is no longer suitable.

Several other indicators may alert you to the fact that the diaper is probably too small now.

If you're experiencing increasingly frequent leaksthis means that the absorption surface is no longer large enough for your baby's morphology and size.

In this case, switch to size 4. The same applies if you notice red marks on your baby's skin when you change him.

How many size 4 diapers should I buy for my baby?

As explained earlier, size 4 diapers are the size your baby will wear the most. So it's perfectly possible to order several packs in advance, as they'll almost certainly all be used.

To reduce the mental workload involved in buying diapers, you can opt for a subscription that will enable you to receive your diapers whenever and wherever you want.

Our table below summarizes the quantities of diapers to buy according to baby's size and age, for each diaper size. Of course, this may vary from one child to another:


Number of packs in size 3

Number of size 4 packs

Number of packs in size 5

from 5 to 7 kg


from 7.1 to 7.5kg



from 7.6 to 9.9kg


from 10 to 10.5kg



+ over 10.5kg


How to choose the best size 4 baby diaper?

Your baby needs to feel comfortable in his diaper, both in terms of the size you choose and the quality of the diaper itself.

In fact, diapers are in direct and permanent contact with your baby's skin, right up to the moment he or she becomes potty-trained. That's why it's so important for your child to choose healthy, soft diapers that he or she feels comfortable in, and that offer good support.

For healthy diapers, it 's essential to pay attention to the diaper's composition. You need to make sure that the diaper does not contain toxic chemicals, endocrine disruptors, perfume, latex or chlorine. To ensure the right composition, you also need to look at the bleaching method used. Most diapers are bleached using the ECF (Elementary Chlorine Free) method, which uses chlorine derivatives. These chlorine derivatives are toxic to your baby's delicate skin.

5% of diapers are bleached using the TCF (Totally Chlorine Free) method. This method guarantees that diapers have been bleached without chlorine or chlorine dioxide. This is the healthiest method for your baby.

For a quality product, it's best to opt for disposable, eco-friendly diapers. In general, they pay more attention to the composition of their products, adopting natural materials, renewable materials, etc...

Ecological and natural diapers are no less absorbent than conventional diapers. They simply use synthetic materials for the absorbent part, whereas ecological diapers use cellulose of natural origin.

You should also beware of marketing claims such as hypoallergenic, dermatologist-tested, etc., as these are obligatory claims that in no wayguarantee the diapers' non-toxicity .

Baby's growing: when to change to a size 5 diaper?

As for when to change to a size 4 diaper, if you notice that your baby is leaking more and more often, that you can no longer close the fasteners, or that his skin gets red marks when you change his diaper, this means that his diaper is too small. You can then turn to size 5 diapers.