Your Go-To Diaper Size Chart—Plus, How to Determine Baby’s Diaper Size
Buying anything for baby that comes in different sizes is tricky since your little one is growing so fast—and diapers are no exception. You want them to fit well, but also not so well that baby outgrows them in a week or two (aka before you’ve used up all the diapers in the box). And, let’s face it, there’s also the poop factor: A too-big diaper can cause just as much of a mess as a too-small one.
“I had to learn the stinky way when it was time to size up on my daughters’ diapers,” says Alexia M., mom of two in Tampa, Florida. “And that’s when their poop started bursting out of them. I called it the poop bomb. The diaper had gotten too small to hold the stink.”
So how do you find the right diaper size for your little one—and avoid the dreaded “poop bomb”? Read on for a handy diaper size chart by weight (including all the popular diaper brands), as well as plenty of expert and real-parent tips on how to find the right fit.
Diaper sizes vary slightly from one brand to the next, but they all use the same basic numerical system. Diaper sizes are numbered starting at 0 or 1, and go up to size 6, 7 or 8, depending on the brand. Some brands also have non-numerical preemie and newborn diaper sizes, plus some brands have diaper styles targeted to different developmental stages. Pampers Baby-Dry diapers, for example, go from size 0 to size 7, while the Pampers Cruisers line, for crawling or walking babies, starts at size 3.
Within each brand, each size represents a baby weight range and is generally designed to fit babies who fall within that range. Sometimes there’s some overlap between sizes, so if baby’s on the upper end of one size, they may also be able to move into the next size.
Using your newborn baby’s weight is a good starting point for finding the right diaper, says Danielle Sees, RN, IBCLC, a pediatric nurse and lactation consultant at the Mother Baby Assessment Center at Providence St. Joseph Hospital in Orange, California. She says most newborns, including preemies, weighing in at less than 7 pounds do best in a preemie diaper, while newborns 7 pounds and over can usually fit well in a newborn diaper.
That said, all babies are different, so your newborn may do better in a preemie diaper for a few weeks—or, if you have a bigger baby, you might skip newborn sizing completely and start with size 1.
Baby’s diaper size is based on a combination of weight, comfort and other factors. First, you’ll want to check baby’s weight against the size chart for your brand of choice. If you don’t know exactly how much baby weighs, that’s okay: Brands include either a weight range or a minimum or maximum weight for each of their sizes, so you can guesstimate.
Finding baby’s size isn’t always as straightforward as checking the chart, however. When we asked parents how they determined the right size diaper for their baby, they focused on two main factors: comfort and absorbency.
“Both of my boys have really sensitive, eczema-prone skin, so the first thing I look for is whether the diaper will be gentle on their skin,” says Jessica N., mom of two in Utah. “I also care a lot about a good fit and strong absorbency.”
Essentially, the diaper that fits baby best is the one that’s comfortable for them to wear and also prevents leaks and blowouts. This might mean buying up or down a size, regardless of what your brand’s size chart says: “I knew it was time to size up when the diapers started leaking overnight, even if the weight range on the box said [my daughter] still fit,” says Francheska S., mom of one in New Jersey.
What size is baby in your favorite diaper brand? Check out our diaper sizes chart to find out.
While baby’s weight is the easiest way to figure out when to size up their diaper, a lot of other factors can come into play. Here are some obvious—and not-so-obvious—signs that it’s time to grab a bigger size the next time you stock up.
- They keep leaking. Frequent leaks are one of the most common signs that baby’s diaper is too small. Nearly all the parents we talked to said that nighttime leaks, blowouts and needing to do extra laundry were their cue to size up.
- The tabs don’t stay closed. You should be able to fasten the diaper tabs easily, says Jenelle Ferry, MD, a board-certified neonatologist and the director of feeding, nutrition and infant development at Pediatrix Medical Group in Florida. If you can’t—or they keep popping open or coming loose—the diaper may be too small.
- The leg holes are too tight. You want a snug fit around baby’s adorably chunky thighs to help avoid leaks, but not so snug it’s leaving marks.
- The diaper’s riding low. Baby’s diaper should rise high enough to cover some of their back, says Sees. Caroline G., mom of three in New Jersey, agrees: “It was time to size up when diapers suddenly felt more like low-rise jeans than functional gear.”
- Baby’s getting more diaper rash. Ferry says you may see an increase in diaper rash if baby’s wearing too-small diapers. According to the American Academy of Pediatrics (AAP), it’s because diapers that are too small (or fastened too tightly) trap extra moisture and are more likely to rub against baby’s skin.
There are so many types of diapers to choose from—not to mention brands. Where do you even start? Here are some tips to help you find the perfect diaper for baby.
- Focus on fit, not numerical size. Baby’s weight can be a useful guideline—but just like adults, babies are all built differently so it’s about fit and comfort too. Don’t get too hung up on what size baby “should” be based on their weight—just get the size that fits best.
- Choose the right life stage. Diapers are often designed for different life stages and milestones, says Ferry: “Many newborn diapers have a color-changing line that can be helpful for determining when baby has peed, [and] as infants get to crawling phases, there are diapers designed to allow for more leg movement while holding in waste.”
- Pay attention to material. Make sure to read up on the materials your brand of choice uses to make their diapers, particularly if baby has sensitive skin. Ferry says different materials can affect baby’s skin in different ways. Be ready to switch to another brand if baby’s getting a lot of diaper rashes or irritation, she adds.
- Consider cost vs. quality. When you’re changing what seems like an infinite amount of diapers a day, it’s tempting to buy the absolute cheapest option you can find. But several of the parents we talked to said they’d rather pay a little more for a good-quality diaper. “Price mattered, but I was willing to invest a bit more for a diaper that could last through a nap and a playdate without a change,” says Caroline G.
- Be open to change. Sometimes it makes sense to switch brands. Sees says that one brand might work better to control leaks than another as baby grows. Caroline G. says she used Pampers Swaddlers for her newborns because of their softness and comfort, but switched over to Huggies Little Movers when her kids became mobile because of their snug fit and leak protection.
Frequently Asked Questions
What size diapers do babies stay in the longest?
This is pretty variable since babies grow at different rates, but Ferry says size 4 diapers fit many babies between 6 and 18 months. This tracks with the parents we talked to, most of whom said their little ones seemed to stay in sizes 4 or 5 the longest.
How to find the right diaper brand for baby?
The short answer? Trial and error. No one brand works for every baby, so you have to decide what’s most important to you—whether it’s absorbency, cost or sensitive skin-friendly materials—and find something that checks off your priority boxes. Here’s another tip: If it’s your first time trying a diaper brand, buy a small package instead of a giant value box to make sure you love it before you invest.
What’s the best disposable diaper?
Ask any parent what the best disposable diaper is, and they’ll tell you something different from that other parent you asked! Many parents we talked to swear by Pampers, Huggies, Coterie, Honest and the Costco Kirkland brand.
How many diapers of each size do you need?
This will vary based on baby’s age and weight, but in general, you should plan to buy more diapers when baby’s in smaller sizes (newborn through size 2 or 3) and fewer when they graduate to size 4 and up. Newborns go through about 10 to 12 diapers per day, while an older baby over 25 pounds might only need 5 to 7. Just don’t do too much stocking up in advance: After all, they grow up so fast!
How are cloth diapers sized?
Most cloth diapers come in small, medium and large sizes, often with options like newborn or preemie to accommodate smaller babies. These sizes are also based on weight ranges, just like disposable diapers. Some cloth diapers are available as one-size-fits-all, with enough adjustability to fit baby as they grow.
How are overnight diapers sized?
Overnight diapers are sized by weight, but typically start with size 3, not size 1. Many babies are sleeping for longer stretches at night by this point and need a higher absorbency diaper: “As babies get older, the volume of their pees may get pretty large overnight,” says Ferry.
Overnight diapers also often go up to larger sizes, like 7 or 8, to accommodate this increased volume and baby’s developmental needs. Most toddlers take longer to be potty trained overnight than during the day, so you might be buying these for a while.
How are swim diapers sized?
Swim diapers are made from different materials than regular diapers and are designed to keep solid waste (aka poop) from leaking into the water. They don’t actually absorb liquids (because otherwise they’d swell up as soon as they hit the water!) so they fit differently and are sized differently than regular diapers. They usually come in small, medium and large sizes, with each size covering one or two regular-diaper sizes.
Please note: The Bump and the materials and information it contains are not intended to, and do not constitute, medical or other health advice or diagnosis and should not be used as such. You should always consult with a qualified physician or health professional about your specific circumstances.
Plus, more from The Bump:
Jenelle Ferry, MD, is a board-certified neonatologist and the director of feeding, nutrition and infant development at Pediatrix Medical Group in Florida. She earned her medical degree from the University of Oklahoma College of Medicine.
Danielle Sees, RN, IBCLC, is a pediatric nurse and lactation consultant at the Mother Baby Assessment Center at Providence St. Joseph Hospital in Orange, California.
Healthy Children (American Academy of Pediatrics), Why Is My Baby Always Getting Diaper Rashes?, December 2024
US Centers for Disease Control and Prevention, Tips for Using Swim Diapers, May 2024
Real-parent perspectives:
- Alexia M., mom of two in Tampa, Florida
- Caroline G., mom of three in New Jersey
- Francheska S., mom of one in New Jersey
- Jessica N., mom of two in Utah
Learn how we ensure the accuracy of our content through our editorial and medical review process.
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