10 Signs on When to Size Up Diapers (2024)

You will know when to size up diapers when your baby’s diaper leaks regularly or has many blowouts. You may also notice red marks, chafing, or a rash. These are signs that the diaper is too tight, and it is time to size up.

When to Size Up Diapers?

1. Diaper Brand Guidelines 

Each diaper brand provides a size chart containing weight guidelines for their diapers. Each size is usually a range, and the sizes often overlap. If your baby is on the higher end of the weight range for a size then it might be time to go up in diaper size. 

Diaper brands also provide information about signs that diaper is too small. Each diaper fits differently, so it is essential to look at the guidelines for your chosen brand. The guidelines will explain that the diaper should sit just below the belly button and have a snug fit.

It is time to size up if the diaper rides low in the front. They will also explain that red marks and leaks mean the diaper is too tight, and you need to size up.

2. Regular Leaks 

If your baby’s diaper regularly leaks, it’s time to move up a diaper size. The diaper may be too small to contain the amount of urine your baby is producing, causing leaks. Bigger diapers have more absorbent material, so the diaper may be too small to absorb the urine, causing leaks. 

Regular leaks will occur if the diaper is too small and fits too tightly. A diaper that is too tight can cause compression leaks. If the diaper is too snug on your baby, it will move and cause gaps as your baby becomes more active.

This leaves room for leaks. A small diaper will leak and wet your baby’s clothes and bed linen. The outer layer will be unable to contain the liquid, soaking the whole diaper.

3. Blowouts 

Blowouts are common, especially for newborns. But if they are happening on a regular basis, then it is time to change diaper size. Diapers have special leg cuffs meant to stop poop from leaking out of the diaper. A diaper that is too small will fit too tightly and cause the poop to push out the sides and top of the diaper.

If a diaper is too small, it will reach maximum absorption quickly and be unable to hold the amount of poop necessary. A bigger size diaper will allow more room for the poop and have more absorbent material. Constant blowouts are a problem as they cover your baby in poop as well as the area around them.

4. Red Marks 

It is time to change diaper size if you notice red marks on your baby’s skin. The diaper is too tight if there are chafe marks on the groin, hips, or waist (1). Diapers usually have flexible side panels that are gentle on your baby’s skin. If these panels are causing red marks then it is your first clue that the diaper is too small. 

Red marks caused by a diaper fitting too tightly can be irritating for your baby and may cause them pain. The marks will get worse as your baby becomes more active, and you will first notice them at the legs, cuffs, and waist. Small diapers don’t hold as much liquid as larger ones, so the leg cuffs can become wet, causing red marks.

5. Diaper Rash 

Diaper rash can be a sign for a diaper that is too small. If a diaper is too small, it will be unable to hold the right amount of liquid. This means that there will be excess liquid on your baby’s skin. That moisture can cause diaper rash.

If the diaper fits too tightly, then the wet parts of the diaper will be in close contact with your baby’s skin. When they move around, this can cause chafing, leading to diaper rash. Diaper rash can be very uncomfortable for your baby and cause red and inflamed skin. 

A small diaper will also have inadequate airflow, which causes a damp environment around the skin. Diaper rash can form quickly in humid and wet conditions.

6. Cannot Connect the Diaper Tabs 

If the closure tabs are closer to the hips than the stomach, then it is time to go up a size in diapers (1). The diaper tabs should close on the front of the stomach to prevent leaks and chafing. 

Some brands have a diaper size-up indicator on the front. There are pictures that show you where the tabs should be and when it is time to move up a size. The diaper should fit straight across your baby’s hips. If the tabs are pulling the diaper up, then the diaper is too small.

If the elastic of the tabs is exposed and touches your baby’s skin, then the diaper is too small. This will also cause a gap between the front and back sides of the diaper and can cause leaks.

7. Tight Waistband 

It is time to move up a diaper size if the waistband of the diaper is too tight. If you insert your finger under the waistband and it feels constricted, then it is too tight. You should be able to insert two fingers under the waistband.  A waistband that is too tight can cause leaks and red marks.

The waistband should sit flush with your baby’s skin and not form a muffin top. If the skin at the waist bulges, the diaper is too tight. This will be uncomfortable but can also result in blowouts. A diaper that is too small will be difficult to close properly and will ride low in the front. This will cause leaks.

8. The Bottom is Not Covered Fully 

Some diapers have a slim fit, so try a different brand if you notice that your baby’s bottom is not fully covered. This can also be because the diaper is too small, and it is time to size up. The cuffs on the legs and along the inside of the diaper should fit along the edge of the bottom and inside the thighs. A diaper that is too small will often pull to one side.

You will notice that you have more leaks and blowouts when the diaper is too small and doesn’t cover your baby’s bottom fully. If the diaper is too big, it will also gape and expose your baby’s bottom. This will also result in leaking, so check the diaper size guide or try a different brand.

9. Baby Went up in Clothes Size 

Your baby is growing rapidly, and they will quickly move through clothes. Outgrowing clothes is an easy way to check whether you need to switch diaper sizes. Newborns only wear newborn clothes for about 3-5 weeks, so if your baby is just over a month old, it might be time to size up to size 1 diapers.

Your baby will go through clothing sizes and diaper sizes quickly during the first 6 months. They will be in size 1 diapers for about 3 months before needing to move to size 2 diapers. This often happens at the same time as they move from 0-3 month clothes to 3-6 month clothes.

Also read: 6 Signs to Stop Changing Diapers at Night

10. Baby Shows Discomfort 

If you are not sizing up diapers at the right time, you will notice that your baby is uncomfortable. If the diaper is too small, you will find your baby fussy and irritable. They may kick their legs and pull at the diaper.

This may be because the diaper is too tight and makes them feel constricted. It could also be irritating their skin and causing painful chafing. A diaper that is too small will also leave your baby feeling wet when it reaches its absorbent capacity.

The leg elastics may also be digging into your baby’s skin which would be uncomfortable. A small diaper would also restrict movement and leave your baby with discomfort when they moved.

FAQ

How to tell if diaper is too small? 

A diaper is too small if it leaks, leaves red marks, or sits low in the front.

How to tell if diaper is too big? 

A diaper is too big if it gapes at the leg cuffs and waist.

How tight should a diaper be? 

A diaper should be snug and not tight. You should be able to insert two fingers under the waistband of the diaper.

When to switch from newborn to size 1 diapers? 

It is time to switch to size 1 if your newborn is leaking out of the diaper and is at the top end of the weight range for newborn diapers.

What size do diapers go up to? 

Diapers go up to size 7.

What size diapers do babies stay in the longest? 

Babies stay in size 3 diapers the longest.

Do blowouts mean the diaper is too small? 

Yes, regular blowouts mean the diaper is too small.

Should diaper tabs overlap? 

No, diaper tabs should not overlap.

Can newborns fit size 1 diapers?

Yes, newborns can fit in size 1 diapers if their weight is within the size 1 range. 

Why is my baby peeing out the back of his diaper? 

Your baby is peeing out the back of his diaper because the diaper is the wrong size.

Why is my baby soaking through diapers at night? 

The diaper may be too small for the amount of urine your baby is producing.