You’ve assembled the crib, the stroller, and the car seat — but if you think you’ve seen the last of tricky baby gear, think again.
For some parents, navigating the diaper aisle can be just as confusing as trying to set up a baby bouncer.
How do diaper sizes work?
Not only can it be hard to choose the best type of diaper for your baby (Cruisers! Snugglers! Swaddlers!), but there’s also no guarantee that your newborn baby, for instance, will fit into a newborn diaper.
That’s one reason why diaper sizes are designed for babies of a certain weight rather than a certain age — but even this rule of thumb doesn’t always work.
“The ‘weight’ on the diaper box isn’t always the best judge,” says one member of the What to Expect Community, Mama_Bee_Gee.
Here’s how pediatricians and real parents suggest figuring out which diapers are right for your baby as he grows.
Diaper size chart by weight
Diaper sizes typically go by weight. But for many parents, diaper shopping can mean trial and error — which is why it’s a good idea not to commit to one brand right away.
“Diaper sizes go by the baby’s weight, but kids are all built differently,” says Gina Posner, M.D., a pediatrician at MemorialCare Medical Group in Fountain Valley, California, and a member of the What to Expect Medical Review Board. “You have to go by the fit, and how the diaper works with their build.”
The following chart is a general sizing guide based on some of the most popular diaper brands on the market.[1]
But you may need to try a few different sizes in a few different brands before you find the best one for your baby.
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Size | Weight |
Preemie | Up to 6 pounds |
Newborn | Up to 10 pounds |
Size 1 | 8 to 14 pounds |
Size 2 | 12 to 18 pounds |
Size 3 | 16 to 28 pounds |
Size 4 | 22 to 37 pounds |
Size 5 | 27 pounds and up |
Size 6 | 35 pounds and up |
Size 7 | 41 pounds and up |
Size 8 | 46 pounds and up |
How to check to see if your diaper has the right fit
Just because you have a diaper that lines up with your baby’s weight doesn’t mean it will be a perfect match.
“Every kid is individual as far as what fits them best,” says Dr. Posner.
In general though, here are a few things to look for:
You should be able to fit two fingers into the waistband. “The diaper should fit snugly without being too tight or too loose,” says Micah Resnick, M.D., a pediatrician with TriHealth in Cincinnati, Ohio, and a member of the What to Expect Medical Review Board. “If the diaper is too loose, it won't absorb well and could irritate your baby's skin.”
The diaper shouldn’t leave red marks on the waist or thighs. If you’re seeing irritation or indentations on your baby’s body, that’s a sign that the diaper is too tight, says Dr. Posner.
The tabs should fasten below the belly button. If the tabs overlap or are too far from the center of the waistband, the diaper may not be the correct size, says Dr. Resnick.
You shouldn’t be experiencing leaks. If your baby is having more leaks or blowouts, the diaper may not be the right size for your little one, says Dr. Resnick.
Remember that you may need to do a little sampling of various diaper sizes and brands before you settle on what works for your little one.
For example, start with a diaper that matches your baby’s weight — or one size larger.
“It’s better to start with a size that’s too big than too small,” says Dr. Resnick. That way, if it’s too big, you can save it for later; if it’s too small, you’ll have to give it away or sell it online.
“It’s nice when people get lots of different types of diapers at baby showers, because then they can try them out and see what fits their baby best,” says Dr. Posner.
Which diaper size to buy for your newborn
If your baby weighs under 6 pounds at birth, you may want to put him in a preemie-sized diaper, which has been specifically designed for babies who are small for their age. (Ask your doctor for a recommendation, though.)
If your little one is under 10 pounds at birth, you can try putting your baby in the newborn-sized diaper. Some newborn diapers are also designed with a special belly button cut-out, which keeps the material away from your baby’s umbilical cord.
If he is 10 pounds or more at birth, you may want to start with a size 1.
Regardless of your baby’s birth weight, resist the urge to stock up on newborn sizes. Babies grow quickly at that age, says Dr. Resnick, and your baby will be a size 1 before you know it.
Signs it’s time to size up in diapers
Babies grow quickly, especially during their first few months of life. If you’re wondering if it’s time to make the switch to a bigger size, here are a few signs:
Your baby is having leaks.
If your baby gets pee on his pants — especially through the legs — the diaper may be too tight, says Dr. Resnick. And if your little one is having poop blowouts up his back, the diaper may also be too snug to hold it all in. In fact, some parents use leakage to determine when they size up.
“Once they get a little small and they start blowing out the top is when I usually switch,” says What to Expect Community parent jmtired. “You can’t always go by weight because some babies are just long.”
Adds another What to Expect parent littlegirlmamax2: “I size up when she starts having 2-3 blowouts.”
The size looks off.
A too-small diaper may have gaps around the legs or waist, or the tabs may look too far away from the center of the waistband, say Dr. Resnick. The diaper material may also bunch up around the groin area.
“There should be room in the bottom,” he says.
There are red marks on baby’s skin.
“If the diaper is too tight, it will pinch the skin or cause irritation where the diaper was,” says Kyle Monk, M.D., a pediatrician at Cedars-Sinai Medical Center in Los Angeles, California, and a member of the What to Expect Medical Review Board. “If you see pinching on the skin when you remove the diaper, it is time to size up.”
How many diapers you will need per size
The number of diapers parents need will vary from baby to baby, but you’ll probably need to change an average of six diapers a day — and, on the high end, up to 12 per day, according to the American Academy of Pediatrics (AAP).[2]
All in all, you should expect to need about 3,000 diapers during your baby’s first year of life, and about 8,000 diapers before he's potty trained, says the AAP. Not all of those diapers will need to be sized newborn or size 1, though.
Use this guide to help you plan how many diapers you’ll need per day for your baby.[3]
Size | Approximate Number of Diapers Needed Per Day |
Preemie | Varies |
Newborn | 8 |
Size 1 | 7 |
Size 2 | 6 |
Size 3 | 6 |
Size 4 | 6 |
Size 5 | 5 |
Size 6 | 5 |
Size 7 | 4 |
Size 8 | Varies |
Keep in mind that newborn babies tend to grow quickly, so they may cycle through sizes more when they’re younger. They may also need more frequent diaper changes during that time.
Numbers aside, you should change your baby every time he pees or poops. That means “every time that line turns blue or you smell a poop,” says Dr. Resnick. “Sitting in wet or soiled diapers can lead to diaper rashes and discomfort.”
- Baby diaper sizing can vary — not only from brand to brand, but from baby to baby. Even babies who have the same weight can fit into different size diapers, depending on their body shape.
- Your newborn baby may not, in fact, need a newborn-sized diaper. Little ones under 6 pounds may do better in a preemie size, while bigger babies (10 pounds and up) may fit better in a size 1. Regardless, it’s a good idea not to stock up on newborn sizes — babies grow quickly during their first few months of life!
- Your best bet is to use trial and error to find the best match for your baby; if he starts experiencing leakage or the skin looks red or pinched, it may be time to size up.
How to choose the right diaper brand for your baby, according to moms
Your sister may have sworn by one brand of diapers; your best friend may swear by another. But the truth is, just like all babies are different, all diaper brands are made a little differently too, says Dr. Posner.
Your best bet is to buy a few different brands (or ask for different types for your baby shower) and see what works best. Here are some tips from other parents.
Check for leaks. The best diapers will be the ones that keep your baby dry, without irritating his skin. That said, some parents recommend sizing up for overnight diapers. “We use Huggies night diapers for bed and do size 5,” says G-Ohana, a member of the What to Expect Community. “During the day we have him in size 4.”
Choose the right material. Diapers should be made from soft, breathable material that won’t irritate your baby’s skin. Some parents advise against scented diapers and/or those that feel rough to the touch. If your baby has sensitive skin, try to avoid diapers with fragrances, lotions, and harsh chemicals, says Dr. Resnick.
Consider the fit. Depending on the size of your baby’s belly or legs, you may find that one brand accommodates his body more than another. Says What to Expect Community parent PEG2022: “Not a fan of the ‘curved fit’ because of how it shapes the waistband — I feel like I spend more time trying to close the diaper.”
“You can try multiple brands and styles to find what works best for your baby,” says Dr. Resnick.
Specialty diaper sizing
Your baby may need a new size diaper for overnight or when he goes swimming with you. Use these size guides to find the right fit.
Swim diapers
Disposable swim diapers tend to come in three sizes: small, medium, and large. While the weights can vary by brand, here’s a general rule of thumb.
Size | Weight |
Small | 13 to 26 pounds |
Medium | 20 to 34 pounds |
Large | 29 pounds and over |
Overnight diapers
Once your baby can sleep through the night, you may want to put him in overnight diapers, which have a snugger fit and are made with more absorbent materials to prevent leaks, says Dr. Resnick. Here’s a general size guide.
Size | Weight |
Size 3 | 16 to 28 pounds |
Size 4 | 22 to 37 pounds |
Size 5 | 27 pounds and over |
Size 6 | 35 pounds and over |
Size 7 | 41 pounds and over |
You should always change your baby’s overnight diaper as soon as he wakes up to prevent diaper rash, says Dr. Monk.
Choosing the right diaper brand and sizes for your little one as he grows may seem like a lot to keep track of, but it's not as complicated as it sounds, and these charts and guidelines can help. But if you're still in doubt that you're making the right choices for your baby, check in with your pediatrician for some advice. Before you know it, you'll be past the diaper stage for good!
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