Diaper count per day is based on AAP voiding norms — most babies need a fresh diaper every 2–3 hours when awake, less overnight. Real numbers vary: newborns often go through 12+ per day; older babies who pee on a schedule may use as few as 4.
Sizing is brand-overlap. Different brands run slightly bigger or smaller; if a diaper leaks, size up. If you see red marks at the leg, size up. Most parents find Pampers and Huggies fit slightly differently — try both.