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This diaper calculator helps parents figure out what size diapers they need to buy, how many, and the cost 💰.

So you are a new parent or about to enter the world of parenting, and you are at a loss in the sea of diaper options 😟. Worry not. Our diaper calculator is just what you need to help you navigate this new path. Keep reading to learn:

  1. How to know what size diaper your baby needs;
  2. How to use our diaper calculator;
  3. How to figure out when to change your baby's 👶 diaper size;
  4. When to change a diaper that is either wet or soiled; and
  5. How to calculate how many boxes 📦 of diapers you will need at different stages of a baby's life.

🔎 Babies have very sensitive skin and should be changed immediately if they soil their diapers. Dealing with complications from not changing a baby immediately can be very uncomfortable for your baby and costly for you.

What size of diaper does your baby need

For many new parents answering the question, "what size diaper does my baby need?" can be a complete puzzle. Firstly, every baby 👶 is different, and so are their diaper needs. The most accurate way of choosing a baby's diaper size is to look at their weight. But judging by weight is not one hundred percent reliable, either. This is because one baby's body shape can differ significantly from another. A tall and slim child can have the same weight as one who is short and husky. As you can imagine, even though these babies' weights may match, the fit of their diapers may differ greatly if they are using the same size.

If your baby is tall and slim, you may find the diaper for his category does not go up as high as it should, and that could cause leakage when their stool is too soft. Going a size higher than the suggested size in this instance may be necessary.

Most famous brands use the sizes given in our diaper size chart below. However, when you choose from bargain brands, you may need to check the packaging to see the suggested size for your baby.

If you are an expectant mother, our pregnancy weight gain calculator may also interest you.

Baby's weight

Diaper size

<= 10 lbs


8–14 lbs


12–18 lbs


16–28 lbs


22–37 lbs


More than 27 lbs


More than 35 lbs


More than 41 lbs


As you can see from our diaper size chart, the sizes tend to overlap. So if the suggested size does not work for your baby, you may choose the next size given in the diaper size chart above.

How to use our diaper calculator

Our diaper calculator allows you to enter your baby's weight to figure out the size of the diapers your baby will need. Since babies grow quickly and, as a result, change diaper sizes just as quickly, you should not stock up too much on any one size.

🙋 Your baby's age has much to do with the number of diapers you will need to buy. This is because as your baby matures, he will begin to use fewer diapers until he has no need for them at all.

Each age group has an average number of diapers a baby will be expected to use. As such, your baby's age, along with the time period you are shopping for, is used to calculate the number of diapers your baby will need for the specified period.

Based on the number of diapers you wish to buy and the cost you enter per box, our calculator will also calculate the number of packages you need. It also generates the money you will spend based on the number of boxes and the cost per box you entered.

If you enjoyed this calculator, be sure to check out our baby percentile and baby formula calculators.

How many diapers does my baby need daily?

The number of diapers a baby needs has much to do with his stage of development. In the following table, we have outlined the average number of diapers a baby will use at different stages of development.

Age in months

Number of diapers per day





3- 8






As is clear from this chart, there is no definite number of diapers per a baby's stage of development. However, the number of diapers decreases as a baby grows older until it is no longer needed. This may happen at different stages for different children.

How to tell if your baby needs a bigger diaper

Have you wondered whether it is time to change your baby's diaper size? Here is how to tell if your baby needs a larger diaper:

  • They are experiencing frequent leaks.
  • There are red marks on your baby's legs or waist.
  • The diaper no longer covers your baby's bottom adequately.
  • The waistband feels too tight — you cannot get two fingers in the waistband comfortably.
  • Their weight is either higher or just below the weight limit for that category.
  • You begin to experience difficulty connecting the waist tabs.


Do I need to change a newborn diaper at night?

Yes, newborn babies will need several diaper changes at night.

In fact, the younger a baby is, the greater the need for nightly diaper changes. Opting not to change a baby's diaper at night means that your baby is more likely to develop diaper rash due to being left in a wet or soiled diaper for too long.

Do I need to change a wet diaper right away?

Cloth diapers need to be changed immediately. However, disposable or gel diapers do not.

Disposable diapers absorb urine and often keep your baby feeling dry even when he has urinated once or twice. As such, the frequency of change is dependent on the type of diaper and how absorbent it is. Nonetheless, frequent diaper changes are better for the health of your baby.

How to do I figure out how many boxes of diaper I need?

To figure out how many boxes of diapers you will need, you should:

  1. Decide on the time period you are buying for.
  2. Check the number of diapers a baby in that stage of development is likely to use.
  3. Check the number of diapers per box.
  4. Multiply the daily number of diapers for that stage by the number of days in that period.
  5. Divide the answer in Step 4 by the number of diapers in the desired box.

How many boxes of diapers do I need for a newborn baby?

Newborn babies typically use 10 to 12 newborn diapers per day. So using the upper limit, you will need 12 × 30 = 360 diapers for the first month. If you intend to buy a pack that contains 192 diapers, you will need two boxes of these diapers in the first month. If a smaller box is available, it may be best to opt for one large and one small.

Adena Benn
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