Quick answer
On the UK-WHO chart, an average (50th centile) boy is 3.5 kg at birth, 9.6 kg and 75.7 cm at 1 year, 18.6 kg and 109.6 cm at 5, 31.4 kg and 138.4 cm at 10, and 66.8 kg and 177.1 cm at 18. Most healthy boys are between the 2nd and 98th centiles.
Plot your son on the chart
Boys’ height chart (cm)
| Age | 2nd | 9th | 25th | 50th | 75th | 91st | 98th |
|---|---|---|---|---|---|---|---|
| Birth | 46.3 cm | 47.9 cm | 49.4 cm | 51.0 cm | 52.6 cm | 54.1 cm | 55.7 cm |
| 3 months | 57.2 cm | 58.7 cm | 60.1 cm | 61.4 cm | 62.8 cm | 64.2 cm | 65.6 cm |
| 6 months | 63.2 cm | 64.7 cm | 66.2 cm | 67.6 cm | 69.1 cm | 70.5 cm | 72.0 cm |
| 9 months | 67.4 cm | 69.0 cm | 70.5 cm | 72.0 cm | 73.5 cm | 75.0 cm | 76.6 cm |
| 12 months | 70.9 cm | 72.6 cm | 74.1 cm | 75.7 cm | 77.3 cm | 78.9 cm | 80.6 cm |
| 18 months | 76.7 cm | 78.6 cm | 80.4 cm | 82.3 cm | 84.1 cm | 85.9 cm | 87.8 cm |
| 2 years | 81.5 cm | 83.7 cm | 85.7 cm | 87.8 cm | 89.9 cm | 91.9 cm | 94.1 cm |
| 3 years | 88.5 cm | 91.1 cm | 93.6 cm | 96.1 cm | 98.6 cm | 101.1 cm | 103.7 cm |
| 4 years | 94.1 cm | 97.0 cm | 99.7 cm | 102.5 cm | 105.3 cm | 108.0 cm | 110.9 cm |
| 5 years | 100.3 cm | 103.5 cm | 106.5 cm | 109.6 cm | 112.6 cm | 115.7 cm | 118.9 cm |
| 6 years | 106.0 cm | 109.4 cm | 112.7 cm | 115.9 cm | 119.2 cm | 122.4 cm | 125.9 cm |
| 7 years | 111.3 cm | 115.0 cm | 118.4 cm | 121.9 cm | 125.4 cm | 128.8 cm | 132.5 cm |
| 8 years | 116.6 cm | 120.5 cm | 124.2 cm | 127.8 cm | 131.5 cm | 135.2 cm | 139.1 cm |
| 9 years | 121.4 cm | 125.5 cm | 129.4 cm | 133.3 cm | 137.2 cm | 141.1 cm | 145.2 cm |
| 10 years | 125.7 cm | 130.1 cm | 134.2 cm | 138.4 cm | 142.6 cm | 146.7 cm | 151.1 cm |
| 11 years | 129.7 cm | 134.5 cm | 138.9 cm | 143.4 cm | 147.9 cm | 152.3 cm | 157.0 cm |
| 12 years | 133.6 cm | 138.7 cm | 143.5 cm | 148.4 cm | 153.2 cm | 158.0 cm | 163.1 cm |
| 13 years | 138.7 cm | 144.3 cm | 149.5 cm | 154.8 cm | 160.1 cm | 165.3 cm | 170.9 cm |
| 14 years | 145.3 cm | 151.2 cm | 156.8 cm | 162.4 cm | 168.0 cm | 173.5 cm | 179.4 cm |
| 15 years | 152.2 cm | 158.0 cm | 163.5 cm | 168.9 cm | 174.4 cm | 179.8 cm | 185.6 cm |
| 16 years | 157.8 cm | 163.2 cm | 168.3 cm | 173.4 cm | 178.5 cm | 183.6 cm | 189.0 cm |
| 17 years | 161.1 cm | 166.3 cm | 171.1 cm | 175.9 cm | 180.8 cm | 185.6 cm | 190.7 cm |
| 18 years | 162.7 cm | 167.7 cm | 172.4 cm | 177.1 cm | 181.8 cm | 186.5 cm | 191.5 cm |
Length (lying down) under 2 years; height (standing) from 2 years.
Boys’ weight chart (kg)
| Age | 2nd | 9th | 25th | 50th | 75th | 91st | 98th |
|---|---|---|---|---|---|---|---|
| Birth | 2.5 kg | 2.8 kg | 3.2 kg | 3.5 kg | 3.8 kg | 4.2 kg | 4.5 kg |
| 3 months | 5.0 kg | 5.4 kg | 5.9 kg | 6.4 kg | 6.9 kg | 7.4 kg | 8.1 kg |
| 6 months | 6.3 kg | 6.8 kg | 7.4 kg | 7.9 kg | 8.5 kg | 9.2 kg | 9.9 kg |
| 9 months | 7.1 kg | 7.7 kg | 8.3 kg | 8.9 kg | 9.6 kg | 10.3 kg | 11.1 kg |
| 12 months | 7.7 kg | 8.3 kg | 9.0 kg | 9.6 kg | 10.4 kg | 11.2 kg | 12.1 kg |
| 18 months | 8.7 kg | 9.4 kg | 10.1 kg | 10.9 kg | 11.8 kg | 12.7 kg | 13.7 kg |
| 2 years | 9.6 kg | 10.4 kg | 11.3 kg | 12.2 kg | 13.1 kg | 14.2 kg | 15.4 kg |
| 3 years | 11.2 kg | 12.2 kg | 13.2 kg | 14.3 kg | 15.6 kg | 16.9 kg | 18.4 kg |
| 4 years | 13.2 kg | 14.2 kg | 15.3 kg | 16.6 kg | 17.9 kg | 19.5 kg | 21.3 kg |
| 5 years | 14.8 kg | 16.0 kg | 17.2 kg | 18.6 kg | 20.3 kg | 22.1 kg | 24.4 kg |
| 6 years | 16.3 kg | 17.7 kg | 19.1 kg | 20.8 kg | 22.7 kg | 24.9 kg | 27.7 kg |
| 7 years | 18.0 kg | 19.5 kg | 21.1 kg | 23.1 kg | 25.3 kg | 28.1 kg | 31.6 kg |
| 8 years | 19.7 kg | 21.5 kg | 23.3 kg | 25.6 kg | 28.4 kg | 31.8 kg | 36.5 kg |
| 9 years | 21.6 kg | 23.5 kg | 25.7 kg | 28.4 kg | 31.7 kg | 36.0 kg | 42.0 kg |
| 10 years | 23.6 kg | 25.8 kg | 28.3 kg | 31.4 kg | 35.3 kg | 40.3 kg | 47.7 kg |
| 11 years | 25.6 kg | 28.2 kg | 31.0 kg | 34.6 kg | 39.1 kg | 44.9 kg | 53.3 kg |
| 12 years | 27.8 kg | 30.7 kg | 34.0 kg | 38.1 kg | 43.2 kg | 49.7 kg | 58.9 kg |
| 13 years | 30.7 kg | 34.2 kg | 38.2 kg | 43.0 kg | 48.8 kg | 55.9 kg | 65.6 kg |
| 14 years | 34.5 kg | 38.8 kg | 43.5 kg | 49.2 kg | 55.8 kg | 63.7 kg | 73.8 kg |
| 15 years | 39.0 kg | 43.9 kg | 49.2 kg | 55.4 kg | 62.6 kg | 71.0 kg | 81.5 kg |
| 16 years | 44.1 kg | 49.1 kg | 54.4 kg | 60.6 kg | 67.8 kg | 76.1 kg | 86.6 kg |
| 17 years | 48.5 kg | 53.3 kg | 58.4 kg | 64.3 kg | 71.2 kg | 79.1 kg | 89.2 kg |
| 18 years | 51.4 kg | 56.1 kg | 61.0 kg | 66.8 kg | 73.5 kg | 81.3 kg | 91.1 kg |
Boys’ BMI chart
| Age | Underweight (≤2nd) | Healthy weight (2nd–91st) | Overweight (91st–98th) | Very overweight (≥98th) |
|---|---|---|---|---|
| 2 years | ≤ 13.5 | 13.5 – 17.5 | 17.5 – 18.6 | ≥ 18.6 |
| 3 years | ≤ 13.3 | 13.3 – 17.4 | 17.4 – 18.4 | ≥ 18.4 |
| 4 years | ≤ 13.6 | 13.6 – 17.6 | 17.6 – 18.8 | ≥ 18.8 |
| 5 years | ≤ 13.5 | 13.5 – 17.4 | 17.4 – 18.7 | ≥ 18.7 |
| 6 years | ≤ 13.3 | 13.3 – 17.5 | 17.5 – 18.9 | ≥ 18.9 |
| 7 years | ≤ 13.3 | 13.3 – 17.8 | 17.8 – 19.5 | ≥ 19.5 |
| 8 years | ≤ 13.3 | 13.3 – 18.3 | 18.3 – 20.2 | ≥ 20.2 |
| 9 years | ≤ 13.4 | 13.4 – 18.8 | 18.8 – 21.0 | ≥ 21.0 |
| 10 years | ≤ 13.6 | 13.6 – 19.5 | 19.5 – 21.9 | ≥ 21.9 |
| 11 years | ≤ 13.9 | 13.9 – 20.2 | 20.2 – 22.8 | ≥ 22.8 |
| 12 years | ≤ 14.3 | 14.3 – 20.9 | 20.9 – 23.7 | ≥ 23.7 |
| 13 years | ≤ 14.8 | 14.8 – 21.6 | 21.6 – 24.6 | ≥ 24.6 |
| 14 years | ≤ 15.3 | 15.3 – 22.4 | 22.4 – 25.4 | ≥ 25.4 |
| 15 years | ≤ 15.8 | 15.8 – 23.2 | 23.2 – 26.2 | ≥ 26.2 |
| 16 years | ≤ 16.3 | 16.3 – 23.9 | 23.9 – 27.0 | ≥ 27.0 |
| 17 years | ≤ 16.7 | 16.7 – 24.5 | 24.5 – 27.7 | ≥ 27.7 |
| 18 years | ≤ 17.2 | 17.2 – 25.1 | 25.1 – 28.3 | ≥ 28.3 |
BMI values (kg/m²) at each centile on the UK90 reference, at the child’s birthday. Thresholds used by the NHS for individual children.
Boys’ growth milestones
- Most boys almost triple their birth weight by their first birthday.
- Growth slows to about 5–6 cm a year from age 4 until puberty.
- The puberty growth spurt usually starts between about 11 and 14 and can add 7–12 cm a year at its peak.
- Most boys reach adult height by 17 to 18.
Frequently asked questions
What is the average height for a 12 year old boy in the UK?
About 148 cm on the 50th centile, but the range is wide because puberty starts at different ages.
What is a normal weight for a 5 year old boy?
About 15 to 24 kg covers the 2nd to 98th centiles; the average is 18.6 kg.
When do boys stop growing?
Usually between 16 and 18, after puberty ends.
Related tools and guides
Child Growth Chart CalculatorPlot height and weight on a UK-WHO chart.Open tool →Child BMI CalculatorBMI centile for children aged 2–18.Open tool →Percentile Calculator UKHeight, weight and BMI centiles.Open tool →Height Percentile CalculatorChild height centile and adult height.Open tool →Baby Weight Percentile CalculatorBaby weight centile, Red Book style.Open tool →Growth Centiles ExplainedHow to read your child’s Red Book chart.Read guide →
About this page
How this guide works
Values are calculated from the UK-WHO LMS reference (UK90 at birth, WHO 2006 to age 4, UK90 from 4 to 18) at each age shown.
Sources
Medical disclaimer: this guide is general information for adults and is not a diagnosis or medical advice. bmicalculatornhs.net is independent and not affiliated with the NHS. Speak to your GP, pharmacist or another qualified health professional about your own health. Full disclaimer.