Diaper size by weight
Diaper sizes go by weight, not age. This is Pampers' US chart, with the average number of diapers a day in each size and how long babies typically stay in it. The ranges overlap on purpose: when a baby is between sizes, the fit decides.
| Size | Weight | Diapers a day | Months in size |
|---|---|---|---|
| Preemie | Under 6 lb | – | – |
| Newborn | Under 10 lb | Up to 10 | 1.6 |
| Size 1 | 8–14 lb | Up to 9 | 1.7 |
| Size 2 | 10–22 lb | Up to 8 | 2.8 |
| Size 3 | 13–26 lb | Up to 7 | 5.8 |
| Size 4 | 15–34 lb | Up to 7 | 6.8 |
| Size 5 | 20–37 lb | Up to 6 | 5.0 |
| Size 6 | 23–44 lb | Up to 6 | 5.8 |
| Size 7 | 26–50 lb | Up to 6 | 4.1 |
| Size 8 | 30+ lb | Varies | – |
Other brands use similar but not identical ranges, so check the chart on the box. In kilograms, the calculator converts Pampers' pounds (1 lb is about 0.45 kg).
When to size up
Pampers' signs it's time for the next size: your baby is in its weight range and the diaper feels tight, leaves red marks on the skin, or leaks despite a proper fit. A good fit is snug without red marks; you should be able to slide two fingers under each leg opening. Large gaps at the legs mean the diaper is too big, even if the waist feels snug. Expect to size up often in the first year.
How the diaper count works
The calculator lays Pampers' "months in size" end to end from birth (newborn for about 1.6 months, then Size 1 for 1.7, and so on) and uses each size's daily average for the months your baby is likely to spend in it. From your baby's age to the potty-training age you choose, that adds up to a total and a count per size, which is handy for buying ahead. Pampers lists Size 8 as "varies", so after Size 7 (at about 34 months) the calculator keeps Size 7's six a day.
Pampers' figures are averages and many babies use fewer, so treat the totals as an upper-end planning number. Babies grow at their own pace, too: if yours moves up a size early, you'll spend less time in the smaller ones.
When do children stop wearing diapers?
The AAP says children usually show signs of bladder and bowel control between 18 and 24 months, the average age toilet training begins in the US is between 2 and 3, and most children are trained by 4. Signs a child may be ready include staying dry for at least 2 hours at a time or after naps. The calculator counts to 3 years by default; change it to match your plans.