📋 Health Information · Editorial Team
Child Weight Chart UK (Ages 5-12)
For school-age children, the adult BMI chart does not apply. UK clinicians use BMI-for-age centiles instead. This guide converts typical weights to stone, explains the centiles the NHS uses, and puts the school weighing programme in context.
Medical disclaimer: This article is general information, not medical advice. Children's growth is assessed by health professionals using proper charts and measurements. Never put a child on a restrictive diet without professional guidance; if you are concerned about your child's weight, speak to your GP, school nurse, or health visitor.
Why the Adult BMI Chart Doesn't Work for Children
Adult BMI uses fixed cut-offs (18.5 to 24.9 is healthy), but children are moving targets. Body fat naturally rises and falls at different ages: it typically dips around age 5 to 6 (the "adiposity rebound") and climbs again towards puberty. A single number cannot capture that.
Instead, the UK uses BMI-for-age centiles on UK90 reference charts. Your child's BMI is calculated the normal way (weight in kg divided by height in metres squared), then plotted for their exact age and sex to give a centile. That centile is what determines the weight category:
| BMI centile | Category |
|---|---|
| At or below 2nd | Underweight |
| Above 2nd to below 91st | Healthy weight |
| 91st to below 98th | Overweight |
| 98th or above | Very overweight |
Note these are the clinical thresholds used when assessing an individual child. Population statistics (like NCMP reports) use slightly different cut-offs. For younger children, see our toddler weight chart (ages 1-4) and baby weight chart (0-12 months).
Typical Weights in Stone and kg (Ages 5-12)
This table converts kilogram readings (what clinics record) into stone and pounds (what most UK parents picture). These are conversions, not targets; healthy weight depends on your child's height and centile:
| Kilograms | Stone and pounds | Roughly typical of |
|---|---|---|
| 16 kg | 2 st 7 lb | Smaller 5-year-old |
| 20 kg | 3 st 2 lb | Average 5 to 6-year-old |
| 24 kg | 3 st 11 lb | Average 7-year-old |
| 28 kg | 4 st 5.5 lb | Average 8 to 9-year-old |
| 32 kg | 5 st 0.5 lb | Average 10-year-old |
| 36 kg | 5 st 9.5 lb | Average 11-year-old |
| 40 kg | 6 st 4 lb | Larger 11 to 12-year-old |
The "roughly typical" column is only a loose guide. A tall 8-year-old at 32 kg and a shorter 8-year-old at 24 kg can both be perfectly healthy; the centile chart adjusts for height, which is exactly why it beats a simple weight table.
The NCMP: School Weighing in Context
Twice during primary school, your child will be weighed and measured as part of the National Child Measurement Programme (NCMP): once in Reception (ages 4-5) and once in Year 6 (ages 10-11). Trained staff take the measurements privately at school, and parents receive a results letter afterwards.
The letter reports your child's BMI centile and weight category. It sometimes surprises parents, because a child who looks "solid" rather than overweight can sit above the 91st centile. Remember that the letter is a screening snapshot, not a diagnosis, and the measurements are taken in school clothes. Our full NCMP explained guide walks through the letter, the opt-out process, and what support is offered.
If the letter says overweight: stay calm and avoid putting your child on a diet or talking about weight in front of them. For most children, the goal is to maintain weight while growing taller, which naturally brings the centile down. Your GP or school nurse can refer you to free local family programmes.
Healthy Habits That Actually Move the Needle
For school-age children, the NHS focuses on behaviours, not body weight. The habits with the strongest evidence:
- 60 minutes of activity a day for ages 5 to 18, from active play to sport, plus activities that strengthen muscles and bones a few times a week
- Water instead of sugary drinks: swapping one daily sugary drink is one of the highest-impact single changes
- Regular meals including breakfast, which is linked with healthier weight patterns in children
- Enough sleep: 9 to 11 hours for ages 6 to 12; short sleep is consistently linked with higher weight gain
- Less recreational screen time, which displaces both activity and sleep
Make changes as a family rather than singling out one child. Children model what they see, and a household that walks, cooks, and sleeps well benefits everyone.
Frequently Asked Questions
How much should a 7-year-old weigh in stone?
It depends on height and build. A typical 7-year-old might weigh anywhere from about 3st 2lb (20 kg) to 4st 10lb (30 kg). In the UK, health professionals assess children using BMI-for-age centiles rather than a single target weight, so the centile your child follows matters more than the number on the scale.
What is a healthy BMI centile for a child?
For individual assessment in the UK, a BMI between the 2nd and 91st centiles is classed as a healthy weight, the 91st to 98th centiles as overweight, and the 98th centile or above as very overweight. At or below the 2nd centile is classed as underweight.
Why can't I use the adult BMI chart for my child?
Children's bodies change constantly as they grow, so a fixed number cannot work. A BMI of 17 might be healthy for a 6-year-old but underweight for an adult. UK clinicians plot a child's BMI on age and sex-specific charts (UK90) and read the centile instead.
What is the NCMP school weighing?
The National Child Measurement Programme measures the height and weight of children in Reception (ages 4-5) and Year 6 (ages 10-11) at school in England. Parents receive a letter beforehand and a results letter afterwards. It is not a pass or fail test; it helps the NHS plan services and gives you a snapshot of your child's growth.
Should I put my child on a diet if they are overweight?
No. Children should not be put on restrictive diets without professional guidance. For most children above a healthy weight, the aim is to slow weight gain while they grow taller, through family-wide healthy habits. Speak to your GP, school nurse, or health visitor, who can refer you to local family support programmes.