Your baby at 18 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 18 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 | 10.94 kg | 10.15–11.79 kg | 10.23 kg | 9.43–11.13 kg |
| Length | 82.3 cm | 80.4–84.1 cm | 80.7 cm | 78.8–82.7 cm |
| Head circumference | 47.4 cm | 46.5–48.3 cm | 46.2 cm | 45.3–47.2 cm |
Want the number for your own baby? Open the percentile calculator
Sleep at 18 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.
- First stepsGross motorusual window: 8.2–17.6
- Walks wellGross motorusual window: 12–20
- Stacks 2 blocksFine motorusual window: 12–18
- ScribblesFine motorusual window: 12–24
- Two-word phrasesSpeechusual window: 16–24
- Plays pretendSocialusual window: 14–24
- Points to picturesCognitiveusual window: 12–20
Vaccine doses at this age
Routine doses only, from the national schedules as published by each country's health authority. Vaccinations always follow chronological age, even for premature babies.
United States
- Hepatitis Adose 2
United Kingdom
- DTaPdose 4
- Hepatitis Bdose 4
- Hibdose 4
- Polio (IPV)dose 4
- MMRVdose 2
Reference figures, not medical advice. Every baby differs; a check-up answers questions a table cannot.