Diaper sizes by weight.
Diaper size is set by weight, not age. As a rough guide: newborn up to 10 lb, size 1 for 8–14 lb, size 2 for 12–18 lb, size 3 for 16–28 lb, and size 4 for 22–37 lb. Enter your baby's weight for the exact fit.
Enter a weight to see which size fits.
The pack beats any chart, including this one
Brands set their boundaries differently — a size 2 is not the same weight range at every manufacturer, and cut and capacity vary too. The ranges here are the general US figures the major brands broadly agree on, which makes them a good starting point and a poor final answer.
Weigh your baby, then read the range printed on the bag you're actually buying. And trust fit over numbers: leaks and red marks mean size up, whatever the chart says.
The full chart
General US weight ranges. Overlaps are intentional.
| Size | Weight (lb) | Weight (kg) | Notes |
|---|---|---|---|
| Preemie | Up to 6 lb | Up to 2.7 kg | For premature and very small babies. Often only sold in hospitals and larger pharmacies. |
| Newborn | Up to 10 lb | Up to 4.5 kg | Most full-term babies start here. Many outgrow it within three to four weeks, so buy one pack before stocking up. |
| Size 1 | 8–14 lb | 3.6–6.4 kg | The longest-lasting early size for most babies, typically spanning the first couple of months. |
| Size 2 | 12–18 lb | 5.4–8.2 kg | Usually somewhere around 2 to 6 months, though it varies widely with your baby's growth. |
| Size 3 | 16–28 lb | 7.3–12.7 kg | A wide range, so most babies stay in size 3 longer than any other size. |
| Size 4 | 22–37 lb | 10.0–16.8 kg | Often coincides with crawling and early walking, when a better fit around the legs starts to matter more. |
| Size 5 | 27 lb and up | 12.2 kg and up | Commonly used through the toddler year. Many brands also offer pull-up styles from this size up. |
| Size 6 | 35 lb and up | 15.9 kg and up | For older toddlers, including many who are still in diapers overnight. |
| Size 7 | 41 lb and up | 18.6 kg and up | Not offered by every brand. Largely used for overnight coverage in older toddlers. |
Five signs to size up.
- 1Leaks and blowouts are happening regularly
- 2Red marks on the thighs or waist after a change
- 3Tabs only just reach, or fasten at the very edge
- 4The diaper no longer covers the bottom fully
- 5Your baby is at the top of the current weight range
Sizing up is easier to spot when you've been counting.
Frequent leaks are much clearer in a week of logged changes than in memory at 3am. Cradle Log tracks every diaper in one tap, so the pattern is there when you need it.
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Common questions
What diaper size should my baby wear?
Diaper size is set by weight, not age. As a general guide: newborn up to 10 lb, size 1 for 8–14 lb, size 2 for 12–18 lb, size 3 for 16–28 lb, size 4 for 22–37 lb, size 5 from 27 lb, and size 6 from 35 lb. Ranges overlap deliberately, so a baby between two sizes will fit either.
How do I know when to size up?
The usual signals are leaks and blowouts becoming frequent, red marks around the thighs or waist after a change, the tabs having to be fastened at the very edge, or the diaper no longer covering the bottom fully. Any one of these means it is time to go up a size, even if your baby's weight is still inside the current range.
Are diaper sizes the same across brands?
No. Pampers, Huggies, and other brands set their weight boundaries slightly differently, and fit varies in cut as well as capacity. Treat any general chart as a starting point and read the weight range printed on the specific pack you are buying.
Should I buy diapers by age instead of weight?
No. Babies of the same age vary widely in weight, so sizing by age is unreliable. Weigh your baby, or use the weight from the most recent pediatrician visit, and size from that.
How many newborn diapers should I buy before the birth?
Buy sparingly. Many full-term babies outgrow the newborn size within three to four weeks, and some skip it entirely if they are born large. One pack of newborn and one pack of size 1 is a common approach, topped up once you know your baby's actual size.
Can my baby wear a bigger diaper at night?
Many parents size up overnight for extra capacity, and several brands sell overnight-specific diapers for the same reason. A diaper that is too large can gap around the legs and leak, so size up one at most rather than several.
Brand size charts
Diaper sizing is product fit, not medical guidance. If you have concerns about your baby's weight or growth, speak to your pediatrician or health visitor.