Your baby at 21 months
Everything that lines up at this one age — growth figures from the WHO standard, sleep norms, the milestones whose normal window covers this month, and the vaccine doses due. Percentiles are called centiles in the UK; the numbers are identical.
Growth at 21 months
Median means half of babies are above and half below. Being away from the median is not a problem in itself — following your own curve is what matters.
| Median (50th) · Boys | Middle half (25th–75th) · Boys | Median (50th) · Girls | Middle half (25th–75th) · Girls | |
|---|---|---|---|---|
| Weight | 11.55 kg | 10.70–12.46 kg | 10.85 kg | 10.00–11.81 kg |
| Length | 85.1 cm | 83.2–87.1 cm | 83.7 cm | 81.6–85.7 cm |
| Head circumference | 47.8 cm | 46.9–48.7 cm | 46.7 cm | 45.8–47.7 cm |
Want the number for your own baby? Open the percentile calculator
Sleep at 21 months
Ranges, not targets. Healthy babies sit outside them regularly.
- Total per day
- 11 h – 14 h
- One nap
- 1 h – 2 h
- Night sleep
- 10 h – 12 h
Milestones in this window
The window is when a skill usually appears — not a deadline. Appearing later than the window is a reason to mention it at a check-up, not to worry alone.
- ScribblesFine motorusual window: 12–24
- Two-word phrasesSpeechusual window: 16–24
- Plays pretendSocialusual window: 14–24
Reference figures, not medical advice. Every baby differs; a check-up answers questions a table cannot.