Diaper sizes go by weight, not by age. Two babies born the same week can be two sizes apart, and the number on the pack is the only reliable guide.
The Baby Life size chart
Every Baby Life pack prints its weight band on the front. Here is the full range in one place:
- Size 1 — Newborn — 2–5 kg
- Size 2 — Small — 3–6 kg
- Size 3 — Medium — 4–9 kg
- Size 4 — Large — 7–14 kg
- Size 4+ — Large Plus — 10–15 kg
- Size 5 — Maxi — 11–18 kg
- Size 6 — XXL — 18 kg and up
- Size 7 — XXXL — 20 kg and up
- Size 8 — 4X-Large — 22 kg and up
The bands overlap on purpose. A 5 kg baby sits inside both Size 1 and Size 2, and either will fit — which is where the fit test below matters more than the number.
The bands overlap, so use the fit test
When your baby’s weight falls between two sizes, check the diaper already on them:
- Red marks at the waist or thighs after a change — too small. Size up.
- Gaps at the leg cuffs you can slide a finger through easily — too large, and the usual cause of leaks.
- Tabs meeting in the middle — a good fit. Tabs pulled right around toward each other means you have outgrown the size.
- The waistband sits below the belly button and cannot be pulled higher — size up.
Three signs you have left it too long
Most parents size up later than they should, because the current pack is not finished yet. The tells:
- Leaks that started recently — a diaper that worked for months and now leaks most nights is a fit problem, not an absorbency problem.
- Marks that are still visible ten or fifteen minutes after a change.
- Your baby fights the change more than they used to. A tight diaper is uncomfortable to put on.
Night is a different size question
Plenty of babies wear one size during the day and the next size up at night. A slightly larger diaper holds more, and twelve hours is a long time. If your mornings involve a change of sheets, try sizing up for nights only before you change anything else.
When to move to pants
Weight is not the trigger — mobility is. Once a change turns into a wrestling match, pull-up pants are usually easier for everyone. Baby Life Pants start at Size 3, so you can switch at any point from about 4 kg onward without leaving the size you already know.