Size is the decision that most affects whether a diaper works or not. A diaper that is too small leaves marks and leaks at the back; one that is too big leaks at the legs and gets used up in unnecessary changes. And because weight ranges overlap between sizes and vary between brands, the choice is not always obvious. This guide brings together the size chart for the brands we sell, the signs that it is time to change and a simple way to plan your purchases by stage.
Weight or age: what counts
Weight. The age shown on some packs is only a guide, because two 6-month-old babies can weigh 6 kg and 9 kg. Always use the current weight, and when your baby is on the border between two sizes, choose based on body shape: babies with fuller thighs fit better in the larger size, while slim, long babies can stay longer in the smaller one.
Diaper size chart by weight and brand
Ranges given by the manufacturers for the products we sell. Notice how the same number corresponds to different weights depending on the brand, and how each brand overlaps its ranges on purpose.
| Size | Dodot Sensitive | Dodot Bebé Seco | Dodot Activity | Moomin Baby | Bambo Nature |
|---|---|---|---|---|---|
| Size 0 | 1-2.5 kg | 1-3 kg | |||
| Size 1 | 2-5 kg | 2-5 kg | 2-4 kg | ||
| Size 2 | 4-8 kg | 3-6 kg | 3-6 kg | ||
| Size 3 | 6-10 kg | 6-10 kg (7-11 kg Extra Absorption) | 7-11 kg (Size 3+) | 5-8 kg | 4-8 kg |
| Size 4 | 9-14 kg | 10-15 kg (Size 4+) | 10-15 kg (Size 4+) | 7-14 kg | 7-14 kg |
| Size 5 | 11-16 kg | 11-16 kg | 12-17 kg (Size 5+) | 10-16 kg | 12-18 kg |
| Size 6 | 13 kg or more | 14 kg or more | 14-19 kg (Size 6+) | 12-24 kg | 16 kg or more |
| Sizes 7 and 8 | 18 kg or more (Size 7), 19 kg or more (Pants Size 8) |
Two useful takeaways from this chart: Moomin Baby and Bambo Nature run one size "smaller" than Dodot (Moomin's Size 3 covers 5-8 kg, Dodot Sensitive's Size 3 covers 6-10 kg), so if you switch brands, check the weight rather than the number. And Dodot's "+" sizes (Size 3+, 4+, 5+, 6+) are slightly larger, more absorbent versions of the base size, designed for babies at the top of the range or for night-time.
You can see the exact ranges for each product in the Dodot, Moomin Baby and Bambo Nature collections.
How to check the size is right
After fastening the diaper, do four checks that take ten seconds:
- Waist: two fingers fit between the diaper and the tummy, and the diaper sits just below the belly button.
- Tabs: they fasten within the marked area, without stretching to the limit or overlapping in the middle of the tummy.
- Legs: the elastic barriers face outwards and sit in the groin with no gaps or creases.
- Bottom: the diaper covers the bottom completely, with the back coming up higher than the front.
Six signs the diaper is too small
- Red marks on the waist or thighs that do not fade within a few minutes of taking the diaper off.
- Leaks at the back, especially at night or after a long nap. This is the most reliable sign: the diaper fills up before your baby wakes.
- The tabs only just fasten or no longer reach the marked area.
- The diaper sits well below the belly button and the back does not cover the bottom.
- It fills up very quickly, with the wetness indicator changing colour in less than two hours during the day.
- Your baby is in the last kilo of the range. Even without signs, it is a good idea to have the next size at home.
And the two signs it is too big: leaks at the legs while the diaper is still almost dry, and a visible gap at the groin when your baby is lying down.
When to change size (and how to make the transition)
The rule that works best: change when the first clear sign appears, not when your baby reaches the maximum weight. The ranges overlap precisely to allow you to move early. In practice:
- If your baby is 1 kg from the upper limit and there are no signs yet, buy a small pack of the next size to keep at home.
- If leaks appear at night but the day goes well, use the next size just for nights for one or two weeks, then switch completely.
- If marks or leaks at the back appear, change straight away, even if there are still 500 g to go before the limit.
- Use up the old pack on daytime changes, which are shorter, and keep the new one for naps and nights.
How many times does a baby change size? Typically five: Size 1 in the first month, Size 2 from the first month until the third or fourth, Size 3 until around 8 to 10 months, Size 4 for the rest of the first year and much of the second, Size 5 and Size 6 until potty training. Every baby has their own pace; go by weight, not the calendar.
Size and diaper rash
A diaper that is too small squeezes and creates friction on the thighs and waist, where the skin becomes damp and irritated. A diaper that is too big lets urine spread and prolongs contact with the skin. If diaper rash always appears in the same place (the thigh creases, for example), size is the first suspect, before the brand or the cream. The article on diaper rash: prevention and treatment covers the rest.
Planning your purchases by size
Since the price per diaper rises with size and large packs only pay off if they get used up, planning makes a difference to your budget:
| Size | Typical duration | Diapers per day | How to buy |
|---|---|---|---|
| Size 1 | 3 to 6 weeks | 8 to 10 | Small and medium packs; never a box before the birth |
| Size 2 | 2 to 3 months | 7 to 8 | First large box, once you have settled on a brand |
| Size 3 | 3 to 5 months | 6 | Large boxes; this is the cheapest size per unit |
| Size 4 | 6 to 10 months | 5 to 6 | Large boxes; consider Size 4+ for nights |
| Size 5 and Size 6 | until potty training | 4 to 5 | Large boxes; consider diaper pants once your baby walks |
For the cost in euros per stage, see how much diapers cost per month, and for quantities by age, how many diapers a baby uses per month. The choice between a small pack and a large box is explained in cheap diapers in Portugal.
Frequently asked questions
My baby is between two sizes. Which one should I choose?
During the day, the smaller one, if it does not leave marks; at night, the larger one. If you have to choose just one, go for the larger, because leaks at the legs can be solved by adjusting the barriers, whereas leaks at the back cannot.
Are sizes the same across all brands?
No. Moomin Baby's Size 3 (5-8 kg) corresponds to a high Size 2 or low Size 3 in Dodot Sensitive (6-10 kg). When switching brands, look at the weight, not the number.
What does Size 4+ or Size 5+ mean with Dodot?
It is a version of the base size with greater absorbency and a slightly larger cut, designed for babies at the top of the weight range and for night-time.
When should we switch to diaper pants?
When your baby starts crawling well or walking and changing them lying down becomes a struggle, usually between 9 and 14 months. Bambo Nature Pants start at Size 4 (7-12 kg).
Newborn: Size 0 or Size 1?
Size 1 for almost all full-term babies; Size 0 is for premature babies or babies under 2.5 kg. We go into more detail in newborn size diaper vs Size 1.
Summary
Choose by weight, check the fit at four points, change at the first clear sign instead of waiting for the maximum weight, and use the overlapping ranges to your advantage: smaller size by day, larger at night, while the old pack runs out. With the brand chart above, switching brand or size stops being a guessing game.
