Enter both heights and the time between measurements to see the growth rate.
Height velocity
0 cm/year
- Time between measurements
- –
- Velocity in inches
- –
- Context
- –
A single velocity is a screening aid, not a diagnosis. Plot growth on the appropriate chart and interpret with the child’s pubertal stage, parental heights and clinical picture.
Height Velocity Calculator
This calculator works out how fast a child is growing — their height velocity, in centimetres per year — from two height measurements and the time between them. Growth rate often tells you more than a single height reading, because a child who is short but growing at a steady, expected pace is very different from a child whose growth has slowed or stalled.
What is height velocity?
Height velocity is the speed of growth, expressed as centimetres gained per year. It changes with age: very fast in infancy, steady through childhood, then a distinct acceleration (the pubertal growth spurt) before slowing to a stop as final height is reached. Clinicians plot velocity on age- and sex-specific charts because the same number can be normal at one age and concerning at another.
How this calculator works
The formula is simple:
height velocity = (current height − previous height) ÷ time between measurements in years
- If you enter dates, the interval is the number of days between them divided by 365.25.
- If you enter months, the interval is months ÷ 12.
- Heights in inches are converted to centimetres (1 in = 2.54 cm) before calculating, and the result is also shown in inches per year.
The optional pubertal stage and age only affect the plain-language context shown with the result. They don’t change the velocity itself.
Typical growth rates
These are approximate figures from population studies. Exact values vary by chart, population and how measurements were taken, so treat them as orientation rather than cut-offs.
| Stage | Approximate growth |
|---|---|
| First year of life | about 25 cm/year |
| Second year | about 10–12 cm/year |
| Third year | about 7–8 cm/year |
| From about 4 years to puberty | typically 5–6 cm/year (roughly 4–7 seen in healthy children) |
| Pubertal growth spurt (peak) | roughly 8–10 cm/year |
| Approaching final height | 2 cm/year or less, slowing to zero |
Getting accurate measurements
Measurement error is the biggest source of misleading velocities, so technique matters:
- Use the same stadiometer (or the same wall-mounted method) each time.
- Measure without shoes, with heels together, back straight and head level, and take the reading at full stretch.
- Measure at a similar time of day, because height can vary by about a centimetre between morning and evening.
- Where possible, have the same person measure each time, and take the average of two or three readings.
Why short intervals are unreliable
A small error in either measurement is magnified when it is scaled up to a full year. An error of half a centimetre on each reading can shift a velocity taken over three months by several centimetres per year. That is why the calculator warns you when the gap is under six months. Twelve months between measurements is usually the most useful interval, and the calculator won’t accept gaps under four weeks.
Frequently asked questions
What is a normal height velocity for a child?
It depends on age and pubertal stage. Between about 4 years and puberty, healthy children typically grow around 5–6 cm a year. During the pubertal growth spurt the peak is roughly 8–10 cm a year, and growth slows again as final height approaches.
How far apart should the two measurements be?
At least six months, and ideally twelve. Shorter gaps magnify measurement error when the result is converted to centimetres per year.
Does this calculator diagnose a growth problem?
No. It calculates a rate and gives general context. Growth concerns are assessed by plotting height and velocity on the correct chart and considering pubertal stage, parental heights, weight and the child’s health.
Why does the result depend on pubertal stage?
Growth rate changes dramatically through puberty, so the same velocity can be reassuring in one stage and low in another. If you don’t know the stage, leave it as “Not specified” and you’ll get general guidance.
What if the current height is lower than the previous one?
Children don’t shrink, so a lower reading almost always means a measurement error. Re-measure before drawing any conclusion.
Medical disclaimer
This calculator is an educational and screening aid for parents and healthcare professionals. It does not diagnose a growth disorder and does not replace assessment by a doctor. Concerns about a child’s growth should be discussed with a GP, paediatrician or paediatric endocrinologist.
Sources & references
- Rikken B, Wit JM. “Prepubertal height velocity references over a wide age range.” Archives of Disease in Childhood, 1992. adc.bmj.com
- Lee JH, et al. “Factors affecting height velocity in normal prepubertal children.” Annals of Pediatric Endocrinology & Metabolism, 2018. pmc.ncbi.nlm.nih.gov
- Royal College of Paediatrics and Child Health. UK-WHO growth charts. rcpch.ac.uk
- World Health Organization. Child growth standards. who.int