Do different diaper brands use a standard size chart?

While different diaper bands use a variety of names for their diaper sizes, numerically they are identical. A size 3 is the same size for Huggies, Luvs and Pampers, regardless of branding.

Diaper size is determined not by the actual size of the baby or the inches of the waist, but rather by how much the baby weighs. For example, a baby between 8 and 14 pounds wears a size 1 diaper, while a baby between 22 and 37 pounds wears a size 4 diaper.

Sizes 5 and up provide only minimum weight thresholds, and at that point parents must determine which sizes provide the best fit for their children. On the other hand, nearly any diaper for a baby below 10 pounds is a newborn diaper.