What Is Diaper Sizes?

Updated 2026-08-02 · Soft Care Guide Editorial Team · Reviewed by Editorial Team · Fact Checked

Direct Answer

Diaper sizes (NB, 1, 2, 3, 4, 5, 6 or NB/S/M/L/XL) correspond to baby weight ranges, ensuring fit, comfort and leak prevention.

Key Takeaways

  • Diaper sizes (NB, 1, 2, 3, 4, 5, 6 or NB/S/M/L/XL) correspond to baby weight ranges, ensuring fit, comfort and leak prevention.
  • How it works: Diaper sizes map to weight ranges that vary slightly by brand: NB (2-5kg), size 1 (3.5-6kg), size 2 (5-8kg), size 3 (7-12kg), size 4 (10-14kg), size 5 (12-18kg), size 6 (16kg+).
  • Size 1 typically fits 3.5-6kg babies — check the weight range on the pack
  • Myth: Age determines size. Weight is the guide — sizes span overlapping weights across brands

How Diaper Sizes Works

Diaper sizes map to weight ranges that vary slightly by brand: NB (2-5kg), size 1 (3.5-6kg), size 2 (5-8kg), size 3 (7-12kg), size 4 (10-14kg), size 5 (12-18kg), size 6 (16kg+). The right size seals at legs and waist without marks or gaps. Size up when leaks occur or red marks appear. Overnight sizing may go one up for absorbency.

Examples and Applications

  • Size 1 typically fits 3.5-6kg babies — check the weight range on the pack
  • Red leg marks signal the diaper is too small; gaps signal too big

Diaper Sizes vs. Related Terms

TermWhat it isKey difference
Overnight diapersDiaper SizesOvernight diapers may be worn one size up for extra absorbency and leak protection

Limitations and Common Misconceptions

  • Myth: Age determines size. Weight is the guide — sizes span overlapping weights across brands
  • Myth: One size fits all brands. Weight ranges vary by brand; check each pack
How do I know when to size up?

Signs: red marks on legs/waist, repeated leaks, or the diaper no longer closes fully.

What size diaper does an 8kg baby wear?

Typically size 3 (7-12kg range) — always check the brand's weight chart.

References

  1. Pampers Official - About Pampers — 品牌官方 (accessed 2026-08-01)
  2. AAP HealthyChildren.org - Diaper Rash and Diaper Care — AAP (accessed 2026-08-01)