Find the right diaper size for your baby's weight. Size chart from Newborn through Size 7 with weight ranges and tips.
Choosing the correct diaper size prevents leaks, blowouts, and discomfort. Diaper sizes are based on weight, not age, because babies of the same age can vary significantly in size. Most brands follow a similar sizing chart.
The most common sizes are Newborn (up to 10 lbs), Size 1 (8-14 lbs), Size 2 (12-18 lbs), Size 3 (16-28 lbs), Size 4 (22-37 lbs), Size 5 (27+ lbs), and Size 6 (35+ lbs). Size overlaps are intentional — fit depends on body shape as well as weight.
This calculator recommends a diaper size based on your baby's current weight and provides tips for knowing when to size up. Getting the right fit is key to overnight dryness and blowout prevention. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation. By automating the calculation, you save time and reduce the risk of costly errors in your planning and decision-making process.
The wrong diaper size leads to leaks and blowouts. Too small and the diaper can't hold enough; too large and gaps appear. This quick reference ensures you're always buying the right size as your baby grows. Having a precise figure at your fingertips empowers better planning and more confident decisions.
NB: up to 10 lbs Size 1: 8-14 lbs Size 2: 12-18 lbs Size 3: 16-28 lbs Size 4: 22-37 lbs Size 5: 27-35+ lbs Size 6: 35+ lbs Size 7: 41+ lbs
Result: Size 2 (12-18 lbs)
A 15-pound baby fits best in Size 2 diapers (12-18 lbs). If leaks are occurring or the diaper feels tight, it may be time to try Size 3, which starts at 16 lbs.
Diaper sizes are weight-based because babies of the same age can differ by several pounds. The weight ranges overlap between sizes, giving you flexibility to choose based on fit rather than strictly by the number on the package.
Newborns start in NB or Size 1, move to Size 2 around 2-3 months, Size 3 around 5-6 months, and Size 4 around 12-18 months. Many toddlers use Size 5 or 6 until potty training.
The waistband should sit at the navel. You should be able to fit two fingers between the diaper and baby's tummy. Leg cuffs should be tucked in, not folded. If you notice persistent leaks, check the fit before assuming a size issue.
Signs include: frequent leaks or blowouts, red marks on skin, difficulty fastening tabs, the diaper looking too small, or being at the top of the weight range for the current size. If you notice any of these indicators, try the next size up for a few days to see if the fit and leak protection improve.
Most babies spend the longest time in Size 3 and Size 4. These sizes cover the widest weight ranges and correspond to the slower growth period between 6-24 months.
Size ranges are similar but not identical across brands. Huggies, Pampers, and store brands may differ by a pound or two per size. The weight ranges overlap intentionally.
Yes, many parents find that sizing up for nighttime provides extra absorbency and prevents overnight leaks. Dedicated overnight diapers in the current size are another option.
Most babies only use newborn diapers for 2-4 weeks. Some larger babies skip NB entirely and start with Size 1. Don't stockpile newborn diapers — buy a small pack initially.
If your baby is at the top of one size's range and the bottom of the next, try both. Generally, going up a size is better than staying in a too-small diaper. Fit should be snug but not tight.