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March 17, 2021

How To Quickly And Accurately Figure Out Diaper Sizes For Your Baby

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Quickly Finding The Right Diaper Sizes For Your Baby

Diaper sizes can be very tricky. Below is a simple guide to help you figure out the diaper sizes you will need.

The guide will also provide an average number of diapers you can expect to use, and how many you can expect to use within the next month. It’s a great tool for planning ahead!

What'S my baby's diaper size? Reset

Enter your baby's weight to find out what diaper size your baby is, and how many diapers he/she will need per day.

Your baby's diaper size is:

Average* diapers per day for this size:

Total number of diapers per month

For more detailed results, use our

diaper calculator

diaper size chart

How To Make Sure The Diaper Fits Properly

Babies come in different shapes and sizes, so it would make sense that diapers would fit differently on each baby. Even so, here are a few quick checks to make sure your baby’s diaper fits properly:

Diapers Based On Your Baby’s Weight

when to move up a size in diapers baby weightDiaper sizes are not based on your baby’s age. They are entirely based on your baby’s weight. Therefore, you will want to choose diapers that match your baby’s weight.

It’s easy to weigh your baby. Take off your baby’s clothes and diaper, and while holding your baby, step onto a regular diaper scale. Record the number. Put your baby down safely, and get back onto the scale to weigh yourself without your baby. Subtract the second number from the first number to get your baby’s weight.

Do keep in mind that the weight ranges of some diapers may overlap, which means that your baby may fit into two sizes. If your baby is long and slim, you may prefer to go with the smaller of the two sizes for the best fit. If your baby is a little huskier, choose the bigger size.

Diaper’s Waistband Under Your Baby’s Belly Button

Your baby’s diaper waistband should fit just under your baby’s belly button.

A properly fitting diaper should come just slightly under your baby’s belly button. If the diaper is fitting a little more like a low rise, it’s time to move on up in size.

No Gaps On The Leg Cuffs

Gaps in a diaper mean leaks and blowouts. Make sure there are no gaps by running two fingers just inside the leg cuffs to get them in the proper position.

No Red Marks On Baby’s Body

when to move up a size in diapers red marks on legs

After your baby’s diaper is fastened, you should be able to fit two fingers under the waistband. If you are able to do this, it means the diaper is fitted properly — not too snug, not too loose.

The elastic on the legs should also not be too tight. When you take the diaper off, you shouldn’t see any red marks. If you do see red marks, this is usually an indication to move up in size.

Diaper Calculator

Our calculator uses data provided by the CDC's Baby Growth Charts and the diaper manufacturer's sizing and usage charts. CDC data is based on the average growth rate of a child.

However, not all children are the same. Please use the data provided as a general estimate to help you plan your diaper purchases.

Disposable Diaper Calculator Refresh

Add your baby's age & weight to calculate the number of diapers you will need during your first year. If you're still pregnant, please estimate your baby's weight.

Enter birthday instead
Estimate baby's weight

How many diapers per day?

0-3 MONTHS10
3-6 MONTHS8-10
6-9 MONTHS6-8
9-12 MONTHS6-7
12-18 MONTHS5-6
18-36 MONTHS4
Diaper usage is based on your baby's age. The younger your baby. the more diapers will be used per day.

What size diaper to choose?

SIZE 18 - 14 LBS
SIZE 212 - 18 LBS
SIZE 316 - 28 LBS
SIZE 422 - 37 LBS
Diaper sizes are based on your baby's weight.

Here's a helpful chart of expected weight gain over the next 6 months. Hover over the chart for more details.

Amazing Savings For New & Expecting Parents


Diapering seems so easy at first glance, but it can get confusing and frustrating. Here are a few helpful posts to help you figure things out.


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