Choosing the right diaper size: buying guide

In collaboration with Rokiyah Hosen Professional proofreading


From birth to around 2/3 years, your baby will need diapers. It's also during this period that your baby will grow and his diaper size will change. In fact, as your baby grows, it's essential to change diaper sizes too, so that they remain adapted to his morphology and don't leak. What size should you choose for your baby? How do you know if you should go up to the next size? We answer all your questions in this article.


How to choose the right diaper size for your baby?

Here's a guide to help you choose your diaper size:




Diaper size 1

From 2 to 5 kg

For newborns, up to 2 or 3 months of age

Diaper size 2

From 3 to 6 kg

For newborns up to about 3 months old

Diaper size 3

From 4 to 9 kg

3 to 6 months 

Diaper size 4

From 7 to 18 kg

6 to 10 months

Diaper size 4+

From 9 to 20 kg

From 10 months to 18 months

Diaper size 5

From 11 to 25 kg

For babies over 18 months

Diaper size 6

After 2/3 years, when your baby is potty-trained, we recommend training pants


For premature or smaller babies, there are also size 0 diapers for babies weighing around 1 to 2 kg.

Depending on its weight

To choose the right diaper size, you need to take into account your baby's weight and morphology.

As you can see from the chart, diaper sizes overlap. In fact, weight isn't the only reference you need to take into account when choosing your diapers.

Depending on its size

Some babies weighing 5 kg will be comfortable in a size 2 diaper, while others will be perfectly uncomfortable in a size 3.

In case of doubt, if your baby falls between two sizes, it's best to take the next size up. 

Age is not the deciding factor when it comes to choosing the right diaper size for your baby's bottom. Every baby has his or her own particular build, and some are smaller than others.

After 3 years: training pants

After diapers, it's time to move on to training pants for your baby. It's the perfect mix between a diaper and classic underwear to help babypotty train.

It slips on like panties, but has a diaper-like absorbent fabric to keep your child dry until the next diaper change. This gives your child greater freedom of movement, and protects him from all those little everyday accidents!

How do I check that the diaper is the right size?

To ensure that your diaper is the right size, here are a few things to consider:

  • When a diaper is the right size, the elastic waistband reaches below your navel;
  • On the legs, the elastic bands should be slightly tightened;
  • When it's time to remove your baby's diaper, if you notice red marks, it means the diaper is too small.

There are several things to consider when choosing the right diaper size. First of all, you need to make sure that your baby is neither too tight, which could make marks on his skin and hinder his movements, nor too loose, which could lead to leaks.

A tip for checking that your baby's diaper is the right size: simply check that you can fit two fingers between your baby's tummy and the diaper. If the fasteners cross, it also means that the diaper is too big, and conversely, if the fasteners are too close, it means that the diaper is too small and squeezes your baby too much.

As a general rule, if you don't notice any leaks, you've chosen the right size. 

When should I change my baby's diaper size?

As your baby grows, you need to change his diaper size. But when exactly should you change it? 

There are several signs that tell you it's time to upgrade:

  • If you can no longer slip two fingers under the waistband of the diaper after lputting it on your baby;
  • If your baby's bottom is not completely covered, you can switch to the next size up;
  • If you notice red marks on your baby's tummy or thighs, it means that the diaper is too tight and that you should choose the next size up;
  • If your baby is prone to diaper rash, it's likely that your diapers are too small;
  • If your baby himself gives you the impression of being embarrassed by his diaper (for example s'he pulls on it);
  • If the diaper's adhesive elastics reach the center of the belt.

How many diapers does baby use every day?

Babies use different numbers of diapers at different ages. In fact, in the first few months of a baby's life, diapers need to be changed very regularly (every two hours or so), or with every bowel movement. It's very important to change your baby's diapers regularly, as this will help prevent diaper rash and other redness that may appear on your child's bottom and/or thighs.

On average, it is estimated that during the first six months, diaper changes are very frequent, with around six to eight diapers a day. This figure drops to five diapers a day between six months and a year, then to 3/4 diapers a day between one and two years, and finally to 2-3 until your child is potty-trained.

These are averages, of course, as every baby is different. 

Are leaks linked to the size of the diaper?

Leaks can occur for a number of reasons. For one thing: 

  • If the diaper is too small or too large, and the wrong size is chosen, leaks may occur;
  • If the size chosen is too small, the diaper will not be able to absorb all the volume of your baby's stool and urine;
  • If, on the other hand, the diaper is too large, there may be leaks and stool and urine may leak from the sides, where the diaper is not tight enough;
  • If the leg elastics are not tight enough, leakage may also occur.

What size diaper to choose at birth?

Depending on the weight of your newborn baby, a size 1 diaper may not be suitable. Generally, the choice s is between a size 1 or 2 diaper at birth for a full-term baby. If ultrasound scans show your future child to be healthy, consider buying size 2 diapers in anticipation.

In any case, even if baby wears a size 1 at the maternity hospital, this purchase won't be wasted because sooner or later he'll have to change to the next size up!

Diaper size FAQ

How do I know the size of a diaper I've already bought?

Diaper sizes are indicated on the packages. You'll also find the average weight of a baby using these diapers, as well as the quantity in the pack.

How do I know if I need to change the size of my baby's diapers?

Your baby grows in growth spurts. To find out when to change your baby's diapers, please refer to our diaper size guide. Signs such as red marks when changing diapers should tell you that the diapers have become too small.

How do you know if your baby's diaper is too small?

If when you change your baby you notice red marks on the bottom, thighs or waistband of the diaper, this means that the diaper is too tight and therefore too small. If you also notice leaks, they may be due to a lack of absorption if the diaper is too small.


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