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Baby & Kids' Clothing Size Chart by Age

Baby clothing sizes are labelled by age but babies grow at different rates. Here's how to convert age to size when buying preloved.

By IPF Editorial Team · Last updated 25 July 2026

Why age-based sizing isn't exact

Baby and kids' clothing is usually labelled by age (e.g. 6–9 months, 2–3 years), but babies of the same age can vary a lot in height and weight. When buying preloved, the age on the label is a starting point, not a guarantee of fit — always check the seller's listed measurements or ask for them if they're not given.

Age-to-size chart

  • Newborn (0–3 months) — up to ~60 cm / 3–6 kg.
  • 3–6 months — ~60–67 cm / 6–8 kg.
  • 6–9 months — ~67–72 cm / 8–9 kg.
  • 9–12 months — ~72–80 cm / 9–10.5 kg.
  • 12–18 months — ~80–86 cm / 10.5–12 kg.
  • 18–24 months — ~86–92 cm / 12–13.5 kg.
  • 2–3 years — ~92–98 cm / 13.5–15.5 kg.
  • 3–4 years — ~98–104 cm / 15.5–17.5 kg.
  • 4–5 years — ~104–110 cm / 17.5–19.5 kg.

Sizing tips when buying preloved

  • If your child is tall or heavy for their age, size up rather than going by age alone.
  • Ask the seller for the brand and size label, not just the age range — sizing varies between brands.
  • For fast-growing age ranges (0–12 months), buy slightly ahead of your child's current age.
  • Check the fabric — knits and stretch fabrics are more forgiving of small size mismatches than woven fabrics.

Frequently Asked Questions

Should I buy baby clothes by age or by measurement?

By measurement when possible. Age-based sizing is a useful starting point, but babies of the same age vary in height and weight, so checking the seller's measurements or brand size label gives a more reliable fit.

Should I size up when buying preloved baby clothes?

If your child tends to run tall or heavy for their age, sizing up is usually safer — especially for fast-growing age ranges like 0–12 months, where a size can be outgrown in a few weeks.

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