Seven Signs It’s Time to Change Your Baby’s Diaper Size

Learn how to find the right diaper size for your baby and know when to size up.

Most babies are in diapers until they 2 or 3, which means your child will change diaper sizes many times during their diaperhood. We’re here to give you the lowdown on all things diaper size and fit.

How Does Diaper Sizing Work?

Much like sizing for our clothes and shoes, sizing for diapers varies across brand, infant and diaper type. However, every diaper brand sizes their diapers based on weight instead of age.

As babies grow and change, so do their diapers. While each brand’s size chart varies slightly, you can typically expect diaper sizes to fall under these approximate weight ranges:

Preemie Diaper Size: 6 lbs. and under

  • Newborn Diaper Size: 10 lbs. and under
  • Size 1: 8-14 lbs.
  • Size 2: 12-18 lbs.
  • Size 3: 16-28 lbs.
  • Size 4: 22-37 lbs.
  • Size 5: 27-35 lbs.
  • Size 6: 35 lbs. and over
  • Size 7: 41 lbs. and over — made for older toddlers

How to Get the Right Diaper Fit

You probably noticed that all of the diaper sizes overlap in weight range, so it’s helpful to ensure proper fit and see if your baby needs to size up or down if they fall in that overlap range.

Make sure the diaper’s waistband rests directly under your baby’s belly button. Then check to see if there are any gaps around the thighs or waistband to prevent leakage. After the diaper is on, try to fit two fingers comfortably under the waistband. If you can’t, the diaper is too tight. If you can fit more than two, the diaper is too loose.

How to Get Diaper Sizing Right

So how do you know when it’s time to size up your baby’s diaper? Let’s talk about it.

The diaper is too tight.

As mentioned above, if you’re unable to fit two fingers underneath the legs or waistband, it’s time to size up.

The diaper tabs won’t stay fastened.

If the side tabs on the diaper don’t reach the center waistband or they keep popping open, you probably need a bigger diaper size. On the flip side, if the tabs overlap, your baby’s diaper may be too big. Use the finger trick to see if the diaper feels too loose.

You can’t get the diaper on.

This one may seem obvious, but if you’re having trouble putting the diaper on, it’s probably too small. If you can get the diaper on but it still seems snug, check to see that it covers your baby’s bum fully.