Child Growth Chart Calculator UK — NHS Centile Chart

A centile (also called a percentile) shows how your child's measurement compares to other children of the same age and sex. The 50th centile is the average — half of children are above it and half below. The 9th centile means your child is smaller than 91% of children the same age. All centile bands between the 2nd and 98th are considered within the normal range.

The UK growth chart has nine centile lines: 0.4th, 2nd, 9th, 25th, 50th, 75th, 91st, 98th, and 99.6th. Most healthy children grow between the 9th and 91st centile. A measurement below the 2nd centile or above the 98th centile may warrant discussion with a GP, particularly if it represents a change from previous measurements.

This calculator uses the WHO Child Growth Standards for children aged 0–5 years and the UK90 reference data for children aged 5–18 years. These are the same references used on UK red book growth charts issued to parents at birth. The UK90 data was developed from a nationally representative sample of UK children.

Not necessarily. A child consistently growing along any centile line — even a low one — is usually healthy. The most important thing is that growth is consistent over time. Concern arises when a child crosses centile lines downward (drops more than two centile spaces), shows no growth over several months, or falls below the 0.4th centile. Always discuss concerns with your GP or health visitor.

Yes. The calculator covers ages from birth (0 months) up to 18 years using WHO growth standards for infants and young children. For newborns, weight loss of up to 10% in the first week is normal. After day 14, babies should be regaining and gaining weight. Your midwife or health visitor will monitor this closely in the first weeks.

Boys and girls grow at different rates and reach different final heights and weights, so separate reference data is used for each. Boys tend to be slightly longer and heavier at birth and this gap widens through puberty. The calculator automatically adjusts the reference data based on the sex you select.