Plot your child's height and weight against UK-WHO/UK90 growth chart centiles for ages 2-18
This calculator is for informational purposes only and does not constitute medical advice. It uses simplified UK-WHO/UK90 growth chart data. Always consult a qualified healthcare professional for accurate growth assessment.
Tracking your child's growth is an important part of monitoring their health and development. In the UK, the NHS uses growth charts to plot children's height (or length for under-2s) and weight against age- and sex-specific reference data. For children aged 2 to 4, the UK-WHO growth standards are used, while the UK90 reference data covers ages 4 to 18. Together, these charts provide a reliable picture of how a child's growth compares to a healthy reference population. Growth charts display a series of centile lines that represent the distribution of height and weight in the population. A child on the 50th centile for height, for example, is taller than approximately half of children their age and shorter than the other half. Children naturally vary in size, and any position between the 2nd and 98th centiles is generally considered within the normal range. The key concern is not the absolute centile, but whether a child's growth pattern is consistent over time or shows unexpected changes. Height and weight are assessed separately because they can follow different patterns. A child who is tall for their age may not necessarily be heavy for their age, and vice versa. Significant discrepancies between height and weight centiles, or a child whose growth crosses two or more centile lines, may warrant further investigation by a paediatrician. The Royal College of Paediatrics and Child Health (RCPCH) publishes the official UK growth charts used across the NHS.
To use the child growth calculator: 1. Enter your child's height in centimetres. If you know their height in feet and inches, convert to centimetres (e.g. 4 feet = 122 cm, 5 feet = 152 cm). Measure without shoes, standing against a wall with feet flat on the floor. 2. Enter your child's weight in kilograms. If you know their weight in stones, multiply by 6.35 to convert. Weigh in light clothing for best accuracy. 3. Enter your child's age in years. For children between whole years, use the nearest whole number. The calculator covers ages 2 to 18. 4. Select your child's sex. Boys and girls grow at different rates, particularly during puberty, so sex-specific reference data is essential for accurate comparison. 5. Review the results. The calculator shows height and weight percentiles, centile bands, height-for-age and weight-for-age classifications, and a growth concern assessment that flags measurements outside the 2nd or 98th centile.
This calculator uses simplified UK-WHO and UK90 reference data to estimate height-for-age and weight-for-age centiles. For each age and sex, there is a median (50th centile) value and a standard deviation (SD) that describes the spread of measurements in the reference population. A Z-score is calculated for both height and weight using the formula: Z = (measured value - median) / standard deviation. The Z-score tells you how many standard deviations a measurement is above or below the median. The Z-score is converted to a percentile using the standard normal cumulative distribution function. For example, a Z-score of 0 equals the 50th percentile (average), a Z-score of -2.054 equals approximately the 2nd percentile, and a Z-score of +2.054 equals approximately the 98th percentile. Height-for-age classification: below the 2nd centile is classified as "Short stature", between the 2nd and 98th centile as "Average", and above the 98th centile as "Tall". Weight-for-age follows a similar pattern with "Underweight", "Average", and "Overweight" classifications. If any measurement falls below the 2nd or above the 98th centile, the calculator flags a potential growth concern.
This calculator provides an approximation using simplified reference data. For accurate growth assessment, your child's measurements should be plotted directly on the official UK growth charts by a healthcare professional. Boys and girls follow different growth patterns, especially during puberty. Boys typically have a growth spurt between ages 12 and 16, while girls tend to grow fastest between ages 10 and 14. Final adult height is usually reached by age 16-17 for girls and 18-20 for boys. Growth is influenced by genetics, nutrition, general health, and hormonal factors. If your child's growth is a concern, your GP may arrange blood tests, X-rays (to assess bone age), or referral to a paediatric endocrinologist. Key resources: RCPCH UK growth charts (www.rcpch.ac.uk), NHS information on children's height and weight (www.nhs.uk). If you are concerned about your child's growth, speak to your GP or school nurse.