Which Diaper Size Should I Buy for My Baby's Weight?

Choose a diaper by your baby's current weight, not their age. Babies under 5 kg need New Born, 5 to 8 kg need S, 8 to 12 kg need M, 10 to 14 kg need L, 14 to 17 kg need XL and 17 kg and above need XXL. Weight bands differ slightly between diaper ranges, so always read the band printed on the pack you are buying.

Key Takeaways

• Weight beats age every time. Two nine-month-olds can be 7 kg and 11 kg, which is two different diaper sizes.

• The same letter is not the same size across ranges. Mylo AirPrime S covers 5 to 9 kg while Mylo Regular S covers 4 to 8 kg, so check the pack band, not just the letter.

• Red marks, gaps at the thigh and repeated night leaks are the three real signals to size up, not a birthday.

• When your baby's weight falls between two sizes, go up. A slightly larger diaper leaks less than a slightly tight one.

• Babies under 5 kg need a New Born size with an umbilical cord notch. Mylo's New Born size sits in the Regular pants range, not in AirPrime.

What size diaper should my baby wear right now?

Match your baby's most recent weight to the band printed on the pack. Every size overlaps with the next one by 2 to 3 kg, which is deliberate. It gives you room to finish the pack you have already opened.

Here is the full picture across both Mylo ranges. Note that the letters do not line up exactly.

Age columns are indicative only. Change counts are planning estimates to help you buy the right pack size, not a medical target.

Shop the Regular range by size: New Born, up to 5 kg | S, 4 to 8 kg | M, 7 to 12 kg | L, 9 to 14 kg | XL, 12 to 17 kg | XXL, 15 to 25 kg

Shop the AirPrime range by size: S, 5 to 9 kg | M, 8 to 13 kg | L, 10 to 15 kg | XL, 12 to 17 kg | XXL, 15 to 25 kg

Why does the same letter cover different weights in different packs?

Because the letter is a label, not a standard. There is no national or global rule that says M must mean 7 to 12 kg. Each range is engineered around its own core, elastic and absorbency profile, so the weight band is set for that specific range.

You can see this clearly inside the Mylo range itself.

The practical rule: if you switch between the Regular range and AirPrime, re-check the band before you re-order. Around 9 to 10 kg is where parents most often assume "she was an L last time" and end up with a diaper that is one band too loose.

From XL upward the two ranges use exactly the same bands, so if your baby is already 12 kg or more you can move between Regular XL and AirPrime XL, or Regular XXL and AirPrime XXL, without re-checking the size.

Which size should I start with for a newborn?

Start with New Born, which covers up to 5 kg, if your baby is under 5 kg at discharge. Keep one unopened S pack at home as well.

Two things matter more than the size itself in the first few weeks.

The umbilical cord stump. Until it dries and falls off, usually within one to three weeks, the diaper should sit below the stump so it stays dry and exposed to air. A newborn diaper with a naval notch does this without you having to fold the waistband down every time. Mylo's New Born diaper pants are cut with naval protection, and the New Born tape diapers let you adjust the waist without lifting both legs, which many parents find easier in the first fortnight and during C-section recovery.

Do not over-stock New Born. Most babies outgrow it within four to eight weeks. Buy one large pack at most and put the rest of your budget into S.

A note on AirPrime: the AirPrime range does not currently include a New Born size. Its smallest band starts at 5 kg. If your baby is under 5 kg, use the Regular range New Born size and move into AirPrime S once your baby crosses 5 kg.

If your baby was born preterm or under 2.5 kg, ask your pediatrician or NICU nurse before choosing a size. Standard newborn diapers can gape badly on a very small baby.

How do I know the diaper is the wrong size?

Look at your baby's skin two minutes after you take the diaper off. Skin tells you more than the number on the pack.

Signs the diaper is too small

• Deep red indentation marks on the waist or in the thigh creases that stay visible after removal

• The waistband sits well below the belly button, or you struggle to pull it up fully

• The back sheet feels stretched tight and the side panels look pulled thin

• Leaks from the top of the back, especially when your baby sits up

• Your baby fusses or arches when you fasten it

Signs the diaper is too big

• Visible gaps around the thighs when your baby stands or is held upright

• It slides down when your baby crawls or walks

• Leaks from the leg openings even though the absorbent core still feels dry

• Bulky between the legs, so your baby's gait looks wide

The two-finger test

You should be able to slide two fingers, laid flat, between the waistband and your baby's tummy. Less than that is too tight. More than that, or if the waistband tugs away easily, is too loose.

Why is my baby's diaper leaking, and is size the problem?

Not always. Use this table to find the actual cause before you buy a different size.

My baby is between two sizes. Which one should I pick?

Go up. A slightly larger diaper leaks less than a slightly tight one, and it is far gentler on skin.

There are two exceptions where you should stay with the smaller size for now.

• Slim, long babies. If your baby is tall for their weight, the larger size may gape at the thigh. Stay with the smaller size and watch for red marks instead.

• Newly mobile crawlers. A loose diaper on a crawler slides. If your baby has just crossed into the next band by 100 grams, finish the current pack first.

Body build matters as much as weight. A chunky 11 kg baby with round thighs and a slim 11 kg baby will not fit the same way. Weight gets you to the right shortlist. Thigh and waist fit picks the winner.

When exactly should I move up a size?

Move up when any two of these are true at the same time.

1. Your baby's weight is in the top 1 kg of the current band

2. Red marks stay visible more than 20 minutes after you remove the diaper

3. You have had two or more leaks in the last week that are not explained by a long change interval

4. The waistband no longer clears the belly button

5. The side panels look visibly stretched when fastened

Most babies change size roughly every three to four months in the first year, then more slowly. A simple habit: re-check the size at every vaccination visit, since your baby gets weighed anyway.

How do Indian diaper sizes compare with international Size 1 to Size 6?

Indian packs use letters. Many imported and US brands use numbers. They map roughly like this, but the weight band on the pack is always the final word.

If you shop across brands, ignore the letter or number entirely and compare only the kilogram band.

Does Indian weather change how I should size and change diapers?

Yes, in three practical ways.

Summer and humid coastal cities. Heat rash and diaper rash rise together. A diaper that is even slightly tight traps more heat in the thigh crease. In peak summer, lean toward the looser of two sizes, shorten your change intervals, and build in 15 to 20 minutes of diaper free time a day on a waterproof mat.

Monsoon. The issue here is storage and volume, not sizing. Slower drying pushes many families to disposables full time, so per day counts go up. Store packs sealed and off the floor rather than in an open bathroom cupboard.

North Indian winters. Parents often layer a diaper under thick woollen leggings. Layering compresses the core, and compressed cores leak. Always check the fit over the clothing your baby actually sleeps in, not over a bare tummy.

Do I need a different diaper size at night?

Night leaks are usually a capacity and timing issue before they are a size issue. Try all three of these first.

• Change right before the last feed rather than an hour earlier

• Make sure the waistband sits above the belly button and both leg cuffs are flipped outward

• Check that the diaper is not being compressed under a tight sleepsuit or swaddle

If leaks continue after fixing all three, move up one size for nights only. Running one size during the day and the next size up at night is a normal setup, not a mistake.

Common sizing mistakes to avoid

• Buying by the age printed on the pack. Age is there for convenience and is the least accurate guide on the label.

• Buying a jumbo pack the week before a growth spurt. Buy the smaller pack when your baby is in the top third of a band.

• Assuming the letter carries across brands or ranges. It does not.

• Sizing up to fix a rash. A rash caused by prolonged wetness needs shorter change intervals and barrier care, not a bigger diaper.

• Pulling the waistband extra tight to stop leaks. This is the single most common cause of back leaks and waist marks.

The two minute fit check

Save this and run it every four to six weeks in your baby's first year.

• Weigh your baby, or use the weight from the last vaccination visit

• Read the kilogram band on the pack, not the letter

• Slide two flat fingers between the waistband and the tummy

• Run a finger around both leg cuffs to flip them outward

• Confirm the waistband sits above the belly button

• Remove the diaper after two hours and check for marks that last past 20 minutes

• Note where any leak happened: back, thigh or front

Which Mylo range should I pick?

Once you know your size, this is the only other decision left.

Neither range replaces good diapering habits. Frequent changes, a clean and dry bottom, and a barrier cream where your pediatrician recommends one, do more for skin than any single product feature.

AirPrime XL, 12 to 17 kg: 24 count | 48 count | 96 count

AirPrime XXL, 15 to 25 kg: 24 count | 48 count | 96 count

Regular range New Born, up to 5 kg: Diaper pants, 78 count | Tape diapers, 26 count

Browse the full Mylo diapering range.

Mylo Parents Asked

My baby is 8 kg but M leaks at night. Should I move to L?
Not yet. At 8 kg your baby is in the lower half of the M band, so L will likely gape at the thigh and leak more. First, change right before the last feed and flip both leg cuffs outward. If night leaks continue for a week after that, use L at night and keep M for daytime.

She is 9.5 kg. My friend said L, but the AirPrime pack says M. Which is right?
Both are, for different packs. AirPrime L does not start until 10 kg, so at 9.5 kg your baby is still an M in that range. In the Regular range, 9.5 kg sits in the overlap between M and L. Go by the band on the pack in your hand.

My three month old is only 4.8 kg. Should I still be using New Born?
Yes, if the fit is good and there are no red marks. New Born covers up to 5 kg regardless of age. If your baby is below the expected weight range for their age, raise that at your next pediatrician visit, because it is a growth question rather than a diaper question.

There are red marks on the waist every morning. Is the diaper too small?
Check how long they last. Faint marks that fade within 15 to 20 minutes are normal pressure marks. Deep marks still visible after 20 minutes, or marks that look broken or shiny, mean the fit is too tight. Size up.

Can I switch from the Regular range to AirPrime in the same size?
From XL upward, yes. Both ranges use the same bands, XL 12 to 17 kg and XXL 15 to 25 kg. Below that, re-check, because AirPrime S, M and L each start about 1 kg higher than the Regular equivalents.

AirPrime does not have a newborn size. What do I use for my 3 kg baby?
Use the Regular range New Born size, which covers up to 5 kg and is cut with a naval notch for the cord stump. Move into AirPrime once your baby crosses 5 kg.

My toddler is 19 kg and not potty trained yet. Is there a size for him?
Yes. XXL covers 15 to 25 kg in both the Regular and AirPrime ranges, so 19 kg sits comfortably inside it. Potty training readiness is separate from diaper size and depends on your child's signals, not their weight.

How many packs should I buy before delivery?
One New Born pack and one S pack is enough. Newborns can go through 8 to 12 diapers a day, but most babies outgrow New Born within four to eight weeks and birth weight is hard to predict in advance.

When to speak to your doctor

Diaper size is a comfort and cost question. These are not, and need medical attention.

Contact your pediatrician the same day if you notice:

• Fewer wet diapers than expected, especially in a newborn. A commonly used guide from day five onward is at least six wet diapers in 24 hours. Fewer than this, along with a dry mouth, a sunken soft spot or unusual sleepiness, can point to dehydration

• Diaper rash that is blistering or weeping, or that has open sores, pus, or bright red patches with small spots at the edges, which can suggest a fungal or bacterial infection

• Rash with fever, or rash that is not improving after three days of frequent changes and barrier care

• Blood in the stool or in the diaper

• Swelling, a visible lump, or redness in the groin or scrotum

• Any pressure mark that has broken the skin

Raise it at your next visit if:

• Your baby is not gaining weight along their expected growth curve

• Your baby consistently needs a much smaller or much larger size than typical for their age

• You are dealing with recurring rash despite correct fit and frequent changes

Bottom Line

Buy diapers by your baby's current weight, then confirm the fit with your own eyes: two fingers at the waist, no gaps at the thigh, and no marks that outlast 20 minutes. When your baby's weight sits between two sizes, take the larger one. And whenever you switch between diaper ranges, read the kilogram band again, because the same letter does not mean the same size everywhere.

This article is for general information and is not a substitute for professional medical advice, diagnosis or treatment. Always consult your pediatrician about your baby's health, growth or skin concerns.

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