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When to Move to the Next Size Diapers

Your twins will go through diapers at a rate that will surprise you.

When to move up a diaper size

“Didn’t we just buy a box of diapers?” you’ll ask, surprised, when you see your stock running low. (The answer is always “yes,” by the way.)

One of the challenges of diapers is knowing when to move up to the next size.

Follow the Instructions

Each size diaper corresponds to a weight range to help you know what size to buy for your babies. You’ll find this on the diaper box or package.

What you may not realize is that there is about a two pound overlap between sizes. So you don’t necessarily need to max out the weight range on one size before moving up to the next size.

According this Diaper Fit Guide, these are the size ranges you can expect from diapers:

Newborn: up to 10 lbs (4.5 kg)
Stage 1: Up to 14 lbs (6.4 kg)
Stage 2: 12 – 18 lbs (5.4 kg – 8.2 kg)
Stage 3: 16 – 28 lbs (7.3 kg – 12.7 kg)
Stage 4: 22 – 37 lbs (10 kg – 16.8 kg)
Stage 5: Over 27 lbs (12.2 kg)
Stage 6: Over 35 lbs (15.9 kg)

Watch for Blow Outs

So how do you know when the time is right? The solution is simple:

When your twins start having blowouts and leaks on a frequent basis, it is time to move up to the next diaper size.

This may seem obvious, but in practice, it is not.

Your twins will have a poop that overflows the diaper and you’ll be so busy cleaning it up that you won’t see the pattern that is emerging.

If you hear yourself saying any of these things, it may be time to change diaper sizes:

  • “Again! She had a blowout yesterday…”
  • “What? Another blowout?”
  • “Why does she keep overflowing her diaper?”
  • “I really hate cleaning out these poopy clothes!”

Once you start to see multiple blowouts and on a recurring basis, go ahead and buy the next size diapers.

Baby in Diaper

Diapers Too Small?

If you’re struggling to get the diaper on your babies or they have perpetual red marks around their waste, it is likely time to move to the next size up.

Remember that as babies grow, so does their pee and poop output. If you leave them in a diaper that is too small, it won’t do its job as well as a properly fitted diaper.

Got Extra Diapers?

What if you still have a stack of the current size diaper?

Two solutions: use them on the other twin or give them away.

One of our girls seemed to be having the blowout problem more than her sister. So we moved up a size on one girl and not the other.

If both your twins are ready for the upgrade but you still have left over diapers, don’t worry: diapers make great gifts for other parents-to-be. Yes, even opened packages! You just don’t have to wrap those ones up. The cost of diapers helps parents appreciate any free diapers they can get (even an opened package).

Too Big?

What if we move up a size and the diapers are too big?

Don’t let the “too big” possibility stop you from proceeding. Even if they don’t fit today, your twins will keep growing and they can start wearing them in the near future.

I will say, that with our four kids, we’ve never had the problem of poop leaving a diaper that was too big.

That’s a Lot of Money

Why do diapers cost so much?

Short of changing professions or buying stock in Pampers or Huggies, you may just have to accept the fact that someone’s getting rich at your expense. Diapers are one of the financial curses of twins. Go get yourself a Costco membership and you can save on the diapers.

Cloth diapers can also help reduce your expense over the long term. There will be a higher initial cost but that averages out as you reuse the diapers. There are local cloth diaper services that even handle cleaning and supplying fresh diapers. Just watch your costs or you might be paying more than disposable diapers.

I talk more about diapers and caring for your twins’ potty needs in Chapter 12 of my book, the Dad’s Guide to Raising Twins: How to Thrive as a Father of Twins.

Pictures by Jessica Merz and makelessnoise

Further Reading

Don't forget to pick up a copy of the definitive guide to raising twins. "Dad's Guide to Raising Twins" was written for fathers of twins to help guide you through the first several years with twins. Click here to learn more about the book and get your copy.

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Written by , author of The Dad's Guide to Twins


  1. tanner says

    I recommend cloth diapering. Once you get past the initial purchase they pay for themselves in about 8 months. After that they save about 50 buckets a month.

    • says

      @Tanner – thanks for sharing what has worked with your family. I’ve heard from other parents of twins that used cloth diapers and were happy with that decision too.

  2. nate says

    My kids were little but are now 2 1/2 and are potty trained. We never made it past size 4 in diapers as they haven’t even hit 30 lbs yet. Potty train early as twins will spur each other on and once out of diapers you’re check book will thank you.

  3. Steve H. says

    My Sister-In-Law works at a women’s shelter and often tells me that they run low on diapers all the time. If your kids outgrow a size and you can’t find a fellow parent who could use them, your local women’s shelter may be happy to take them off your hands.

  4. Erin says

    We have one boy that is bigger than the other by a few pounds, so he is the first to size up, and we usually just buy a small package to get him through while his brother catches up. We also use overnight diapers, because nothing can contain these boys overnight, and it’s been that way since they were in size 2s.

    As for money saving – I’ve found that Huggies offers the best coupons ($2 per box) and you can combine coupons, get gift cards for purchasing multiple boxes (with twins you always buy 2 at a time anyway), and use the cartwheel promo at Target. Also – they work better at holding contents and staying on than store brand diapers. By doing this, the per piece price of the diapers is less than Costco or Sam’s 96% of the time.

    **Question** do you have a guide for potty training twin boys? Our boys like to take off their diapers. And we rush them to the potty if we can… but at 22 months, they aren’t really ready.**

    Also- love this site, etc. As a Mom, it’s awesome. Thanks!

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