Enter your baby’s weight to get the diaper size that fits, roughly how many you’ll go through before the next size, and the signs it’s time to move up.
Diapers are sized by weight, not age. Every published chart is a weight range, and the ranges overlap heavily on purpose — an 13 lb baby legitimately fits Size 1, 2 or 3 depending on build and brand. So weight picks the starting size and fit settles it.
The size ranges, the diapers-per-day figures and the months-in-size durations are all from Pampers' published diaper size and weight chart (retrieved 2026-08-07). We use one manufacturer's chart end-to-end rather than blending several, so the weight range, the usage rate and the duration are internally consistent.
Confidence: medium-high for the size ranges, medium for quantity. Duration in a size depends on your baby's growth curve, and other brands cut differently — Huggies, Coterie, Millie Moon and store brands all publish their own ranges and they don't match. Treat the quantity as a planning figure, not a promise, and don't buy more than a box or two ahead of the size you're currently in.
| Size | Weight range | Diapers/day | Typical time in size | Diapers to finish the size |
|---|---|---|---|---|
| Preemie (P) | Under 6 lb | as needed | as needed | — |
| Newborn (N) | Under 10 lb | up to 10 | 1.6 months | about 480 |
| Size 1 | 8-14 lb | up to 9 | 1.7 months | about 460 |
| Size 2 | 10-22 lb | up to 8 | 2.8 months | about 670 |
| Size 3 | 13-26 lb | up to 7 | 5.8 months | about 1,220 |
| Size 4 | 15-34 lb | up to 7 | 6.8 months | about 1,430 |
| Size 5 | 20-37 lb | up to 6 | 5 months | about 900 |
| Size 6 | 23-44 lb | up to 6 | 5.8 months | about 1,040 |
| Size 7 | 26-50 lb | up to 6 | 4.1 months | about 740 |
| Size 8 | 30+ lb | varies | - | — |
Go by weight, not age. Roughly: Newborn under 10 lb, Size 1 at 8–14 lb, Size 2 at 10–22 lb, Size 3 at 13–26 lb, Size 4 at 15–34 lb, Size 5 at 20–37 lb, Size 6 at 23–44 lb and Size 7 at 26–50 lb (Pampers' published ranges). The ranges overlap, so if your baby sits in two sizes, go by fit — leaks and red marks mean move up.
Weight. Age charts exist but they're a rough translation of average growth, and babies aren't average. Two babies the same age can be three sizes apart. Every manufacturer prints weight ranges precisely because age doesn't predict fit.
The published signs are frequent leaks or blowouts (especially overnight), red marks or chafing at the legs and waist, a waistband sitting below the belly button, fastener tabs that no longer reach the middle of the landing zone, and less than two fingers fitting under the waistband. Any one of those means try the next size, whatever the chart says.
Size 4, at roughly 6.8 months, followed by Size 3 and Size 6 at about 5.8 months each (Pampers' figures). The early sizes turn over fast — Newborn averages about 1.6 months and Size 1 about 1.7 — which is why buying cases of Newborn before the birth is the classic registry mistake.
Multiply the per-size daily rate by how long babies stay in it. Newborn runs up to 10 a day for about 1.6 months (roughly 480), Size 1 up to 9 a day for 1.7 months (about 460), and Size 3 up to 7 a day for 5.8 months (about 1,200). Enter a weight above and we'll do it for your baby's current size.
Not comfortably. Size 1 starts at 8 lb; at 7 lb a Newborn diaper (up to 10 lb) will fit better and leak less around the legs. Babies under 6 lb generally need Preemie. The gap matters most at the leg cuff, which is where leaks start.