Baby Percentile Calculator UK
Check your baby’s growth against the UK-WHO standards. Instantly calculate weight, height, and head circumference percentiles to track your little one’s development.
Baby Growth Calculator
UK-WHO Growth Standards (0-4 Years)
Enter age in years and months (e.g., 1 year 2 months)
Enter the measurement from your baby’s check-up
Growth Results
UK-WHO Percentile Estimation
Enter your baby’s details and measurement, then click Calculate to see their growth percentile.
UK-WHO Averages
Approximate median (50th percentile) values for UK babies.
| Age | Boy Weight (kg) | Girl Weight (kg) | Boy Height (cm) | Girl Height (cm) |
|---|---|---|---|---|
| Birth | 3.3 | 3.2 | 49.9 | 49.1 |
| 6 Months | 7.9 | 7.3 | 67.6 | 65.7 |
| 12 Months | 9.6 | 8.9 | 75.7 | 74.0 |
| 2 Years | 12.2 | 11.5 | 87.8 | 86.4 |
| 4 Years | 16.2 | 16.1 | 102.4 | 101.6 |
Baby Growth FAQ
Understanding your baby’s growth charts and percentiles.
A percentile indicates how your baby’s measurement compares to a reference population of babies of the same age and sex. For example, if your baby is in the 75th percentile for weight, it means they are heavier than 75% of babies their age and lighter than the remaining 25%. It is a way to track growth patterns over time rather than a grade or judgment of health.
The UK uses the UK-WHO growth charts. These combine the WHO growth standards for children aged 0-2 years (as breastfed babies are the norm) and the UK 1990 reference data for children aged 2-4 years. This calculator uses data based on these standards to provide accurate percentile estimates for UK babies.
Yes, the 50th percentile represents the median or ‘average’ measurement for a baby of that age and sex. However, ‘normal’ growth covers a wide range, typically anywhere from the 2nd to the 98th percentile. A baby can be perfectly healthy at the 10th percentile or the 90th percentile, provided they are following their own growth curve consistently.
A single low or high percentile is usually not a cause for concern. Health visitors look for the ‘trend’ or pattern of growth. A significant drop across two or more percentile lines (e.g., from 75th down to 25th) or a failure to gain weight/height over time may indicate an issue. Always consult your health visitor or GP if you are concerned about your baby’s growth.
This calculator provides a close estimate based on standard UK-WHO growth data. However, precise clinical assessment requires exact age in days and measurement to the millimetre/gram, plotted on the official physical red book charts. This tool is for educational and tracking purposes and does not replace professional medical advice.