9 years old boy height 137 cm may be normal, or there may be growth retardation, etc., belong to abnormal. 1. Normal: the height of a small child can be calculated using the formula 7 × age + 75, so the standard height of a 9-year-old boy should be 138 cm to 145 cm or so, due to the variability of children’s growth and development, so the height of a 9-year-old boy 137 can be normal. 2. Growth retardation: children’s height is affected by genetic factors, if both parents are taller, then 9 and a half year old boy 137 cm height, there may be growth retardation. In addition if the children picky eating partial food lead to malnutrition, or have a growth hormone deficiency and other diseases may lead to the boy’s height development retardation. 9 and a half years old boy height 137 cm, it is recommended to continue to observe, if you find that children’s height growth is less than 5 centimeters per year, you should go to the hospital in time for examination and treatment.