UK-WHO Growth Centile Calculator
Calculate growth centiles using official UK-WHO growth chart data. Suitable for children from birth to 18 years.
Please Note:
The Growth Centile Calculator provides general information only and is not a substitute for professional medical advice.
Please consult your GP or healthcare provider for personalised guidance about your health.
Child's Measurements
Understanding Centiles
Growth centiles show how your child's measurements compare to other children of the same age and sex:
- 50th centile = Average (50% of children are smaller, 50% are larger)
- 91st centile = Larger than 91% of children
- 9th centile = Larger than only 9% of children
Key centile lines: 0.4th, 2nd, 9th, 25th, 50th, 75th, 91st, 98th, 99.6th
UK-WHO Growth Chart Centile Lines
| Centile | Z-Score | Interpretation |
|---|---|---|
| 0.4th | -2.67 | Very low - clinical review recommended |
| 2nd | -2.0 | Low - may need monitoring |
| 9th | -1.33 | Below average but usually normal |
| 25th | -0.67 | Normal range |
| 50th | 0 | Average / Median |
| 75th | +0.67 | Normal range |
| 91st | +1.33 | Above average but usually normal |
| 98th | +2.0 | High - may need monitoring (especially BMI) |
| 99.6th | +2.67 | Very high - clinical review recommended |
When to Seek Advice
Discuss with Health Visitor/GP
- Weight, height or head circumference below 2nd or above 98th centile
- Crossing downward through two centile lines
- Weight and height centiles more than 2 lines apart
- BMI above 91st centile (overweight) or above 98th (obese)
- Failure to regain birth weight by 2 weeks
Urgent Review Needed
- Measurements below 0.4th centile or above 99.6th centile
- Rapid crossing of three or more centile lines
- Head circumference crossing upward (may indicate raised pressure)
- Associated symptoms: vomiting, lethargy, developmental concerns
- Significant weight loss at any age
Important Notes
Preterm Infants
For babies born before 37 weeks, use corrected age (adjusted for prematurity) until:
- Age 1 year for head circumference
- Age 2 years for weight and length
Specialist preterm growth charts may be more appropriate for very preterm infants.
Measurement Technique
- Weight: Undressed or in light clothing, calibrated scales
- Length: Lying down with infantometer (under 2 years)
- Height: Standing against stadiometer (2+ years)
- Head: Largest circumference using tape measure
Tracking Over Time
A single measurement is less informative than a series of measurements over time.
- Children usually track along a centile line
- Some crossing of lines is normal, especially in first 2 years
- Pattern of growth is more important than single reading
Frequently Asked Questions
UK-WHO growth charts combine World Health Organization (WHO) growth standards for children aged 0-4 years with UK 1990 reference data for older children. They are the standard growth charts used across the NHS in England, Wales, Scotland and Northern Ireland since 2009. They represent how children should grow when breastfed and healthy.
A centile indicates where a child's measurement falls compared to other children of the same age and sex. For example, if a child is on the 75th centile for weight, 75% of children of the same age and sex weigh less than them. The 50th centile represents the median or average. Most children fall between the 2nd and 98th centiles.
Concern may be warranted when: measurements fall below the 0.4th centile or above the 99.6th centile; there is a drop or rise across two or more centile lines; weight and height centiles are significantly different (more than 2 centile spaces apart); or when measurements don't follow the expected pattern. Always discuss concerns with a healthcare professional.
This calculator uses the official UK-WHO LMS parameters to calculate centiles. However, accurate results depend on accurate measurements. For clinical decisions, always use properly calibrated equipment and trained staff to take measurements. This tool is for guidance only and should not replace professional assessment.
Boys and girls grow differently - boys tend to be slightly heavier and taller on average, and the growth patterns differ particularly during puberty. Using sex-specific charts ensures accurate assessment. The UK-WHO charts have separate reference data for males and females.
References
- Royal College of Paediatrics and Child Health. (2009). UK-WHO Growth Charts.
- WHO Multicentre Growth Reference Study Group. (2006). WHO Child Growth Standards based on length/height, weight and age. Acta Paediatrica, 450, 76-85.
- Cole TJ, et al. (1998). British 1990 growth reference centiles for weight, height, body mass index and head circumference fitted by maximum penalized likelihood. Statistics in Medicine, 17, 407-429.
- NICE. (2017). Faltering growth: recognition and management of faltering growth in children (NG75).
- Scientific Advisory Committee on Nutrition. (2011). The influence of maternal, fetal and child nutrition on the development of chronic disease in later life. TSO, London.
Disclaimer
This calculator is provided for educational and informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment.
- Always seek the advice of a qualified healthcare provider with any questions regarding a medical condition.
- Never disregard professional medical advice or delay seeking it because of information from this tool.
- Clinical decision-making should always incorporate the full clinical context, patient preferences, and local protocols.
- The creators of this tool accept no liability for decisions made based on its output.
If you are a patient: please discuss any results with your healthcare provider. This tool is designed for use by medical professionals and may not be appropriate for self-assessment.