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How Do Diaper Sizes Work?

Age, weight, height? How does sizing work?

by Coterie Team

coterie diaper packaging
coterie diaper packaging

This article does not provide medical advice. The information on site is for informational purposes only. No material on this site is intended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your physician, your child’s pediatrician, or other qualified healthcare providers with any questions you may have regarding your or your child’s health.


Choosing the perfect diaper for your baby is essential. We appreciate that no parent wants to select the wrong size and discover that a tight diaper has caused rubbing and soreness on delicate infant skin. Likewise, a diaper that is too loose can cause leaking and more frequent outfit changes, meaning more waste and more laundry for busy parents.


Today, we'll share some tips from experienced moms and dads about how to check the size when you change a diaper, how to pick the ideal size when ordering Coterie’s The Diaper, and why sizing may be unique for every baby.


Do Diaper Sizes Work Based on My Baby’s Age?


If you need help deciding which diaper sizes to purchase, rest assured you are far from alone. The answer is that diapers are sized according to weight rather than age–purely because a newborn baby might weigh significantly more or less than the next, while both are completely healthy.


However, some generic diapers use broad weight ranges for each size, which inevitably means that some infants won’t fit into the ‘standard’ diaper size as they approach the upper or lower end of the scale.


Here at Coterie, we publish a detailed size guide to ensure you are equipped with the information you need to make informed choices about the right size for your baby, recognizing that fit is crucial to optimize diaper performance and minimize the likelihood of leaks and blowouts.


The Diaper Sizing From Coterie


Our sizing guidance is as follows. Every baby is different, and the size you feel fits your baby's body shape is always the best indicator, even if their weight is a little higher or lower.


  • Size N: Up to ten pounds
  • Size N/1: Under ten to twelve pounds
  • Size 1: Eight to twelve pounds
  • Size 2: Ten to sixteen pounds
  • Size 3: Fourteen to twenty-four pounds
  • Size 4: Twenty to thirty-two pounds
  • Size 5: Twenty-seven pounds and above
  • Size 6: Thirty-five pounds and above

Newborn sizes overlap within the initial size categories, but we suggest selecting a 'N' size for any very young baby. Coterie’s The Diaper is carefully engineered with a gentle umbilical cord notch to protect your baby’s skin and provide maximum comfort.


As your baby grows, you may find there is less need to use diaper cream alongside The Diaper due to the extra absorbency, which absorbs up to four times faster than other brands–ensuring you can opt for a true size with less concern about irritated, damp skin.


How Can I Avoid Irritation While Ensuring My Baby’s Diaper Is Secure?


Like every product from Coterie, The Diaper is engineered with exacting attention to detail and precision planning that belies the simplicity of use. Diaper rash and other skin complaints are common in babies and can cause considerable distress and upset for parents and infants alike.


One of the superb features of The Diaper is our 3D Apex Technology—it’s an apparel-grade material that performs and feels like a luxury fabric and is produced with a super-snug leg cuff to support natural movement while helping to minimize spills and leaks.


All this means that if your baby falls between two size categories, you can rest assured their delicate skin is well cared for, and every diaper will meet your expectations until you feel the time is right to transition to the next size up. When you change your baby, simply verifying that there are no visible gaps around their tummy and legs is a great sign that their diaper fits correctly while resting gently on the skin without digging or bunching!