Diaper sizes go by weight, not by age

Read the pounds, ignore the months

Every diaper box prints a weight range, and that range is the whole of the sizing system. Age appears on some packaging as a courtesy and it is the least reliable thing on the box, because two babies of the same age can be a full size apart.

The ranges overlap deliberately. A baby at the top of one size and the bottom of the next will fit both, which is a feature: it means the changeover is a window rather than a cliff, and you can finish the box you have.

Count matters as much as size

A 22 count pack and a 210 count mega box of the same brand are not comparable purchases. The small pack is a top-up or a trial; the mega box is a month of your life committed to one size.

Buying a mega box in the size your baby currently wears is the classic overshoot. By the time you reach the bottom of it, the size below may no longer close. Buying the big box one size up and the small pack in the current size is the usual fix.

What is on this shelf

Worth knowing before you plan around this catalogue: every size from newborn through 7 is listed, and the middle sizes appear in several pack counts rather than one. Stepping up a size does not mean stepping off this shelf.

That has not always been true here, and it may not stay true. What resellers stock and what the brand makes are two different lists, and this page can only speak to the first. The size table below is the general weight guide, not a promise about any particular box.