Child Growth LabChild Growth Velocity Calculator
Compare an earlier and later measurement. Enter height or length, weight, or both to see the recorded change and an annualized or monthly arithmetic rate.
The result is not a percentile, normal range, diagnosis, or prediction. This calculator reports arithmetic change only. It does not calculate WHO infant growth-velocity percentiles.
Pediatric growth calculators based on CDC and WHO growth standards.
How to compare two measurements
Enter the earlier date and measurement first, then the later date and measurement. Complete both sides of at least one pair: height or length, weight, or both. Use the same units and measurement method on both dates.
What growth velocity means
Growth velocity is the rate of change between two dated measurements. This page calculates the arithmetic difference and scales it by elapsed time. It does not compare the rate with an age-, sex-, or puberty-specific reference.
Need a fuller explanation of the rate? Read What Is Growth Velocity in Children?
Recorded change versus annualized rate
Recorded change is the later measurement minus the earlier measurement. The height or length rate divides that change by exact elapsed days expressed as 365.25-day years. Weight is also shown per 30.4375-day average month.
Annualizing is a mathematical conversion, not a forecast that the same change will continue for a full year. Technical constants and canonical Metric inputs remain in the result’s collapsed calculation details.
Why intervals shorter than 6 months need caution
For height or length, this page counts complete calendar months. AAP guidance advises against placing too much emphasis on velocity calculated over less than 6 months because short-term variation and measurement differences can dominate the result. Exactly 6 calendar months does not trigger the warning.
How to measure consistently
Use the same reliable equipment, similar clothing conditions, and the same height or length method. Record dates carefully. For standing height, remove shoes and use a flat wall and firm floor; for weight, use a stable scale on a firm surface.
Do not compare recumbent length with standing height as the same pair. The CDC SAS contract adds 0.8 cm to standing height measured before 24 months and subtracts 0.8 cm from recumbent length measured at 24 months or older. This calculator performs neither conversion and does not infer age or method. Do not adjust a clinical record yourself; if the method changed, an appropriate healthcare professional should decide how to handle it.
What a lower later measurement means
A lower later height, length, or weight remains visible as a recorded decrease. First recheck dates, units, equipment, posture or clothing, and measurement method. The calculator does not infer a medical cause. Discuss an accurate, unexpected pattern with a healthcare professional if you remain concerned.
Babies and WHO velocity standards
WHO publishes actual infant weight-velocity and length-velocity standards for defined early-childhood intervals. Weight standards include 1-month increments from birth to 12 months and 2–6-month increments through 24 months; length standards use 2–6-month increments through 24 months.
This page does not load or implement those WHO velocity tables, z-scores, or percentiles. An arbitrary two-date annualized rate is not a WHO percentile. For attained growth percentiles under age 2, use the WHO Baby Growth Calculator; that page is not a velocity-percentile calculator.
What this result cannot tell you
The arithmetic has no pediatric chart age band, but it cannot define normal or abnormal growth, diagnose a condition, predict future growth, or recommend treatment. Age, puberty, health history, family pattern, and a longer accurate measurement series can change clinical interpretation.
Worked examples
Height or length: January 1, 2025 to January 1, 2026 is 365 days. A change from 120.0 cm to 126.0 cm is +6.0 cm, which scales to about 6.0 cm/year or approximately 2.4 in/year. This is arithmetic, not a normal value or a promise of another 6 cm next year.
Weight: January 1 to July 1, 2025 is 181 days and exactly 6 complete calendar months. A change from 24.0 kg to 25.2 kg is +1.2 kg, approximately +0.20 kg/month and +2.42 kg/year. A height pair over the same dates would not receive the under-6-month warning.
Limitations
- Measurement and date errors flow directly into the calculated change and rate.
- Annualizing can magnify small differences and does not predict future growth.
- The tool does not provide normal ranges, diagnostic thresholds, or treatment advice.
- It does not calculate CDC or WHO velocity percentiles.
- Both height or length measurements must use the same method; do not directly compare recumbent length with standing height.
- The calculator does not apply the CDC SAS 0.8 cm conversions or support self-adjusting a clinical record when measurement methods change.
References
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Helpful context
Frequently asked questions
What is child growth velocity?
It is the rate of change between two dated measurements. This calculator reports the recorded difference and arithmetic rates; it does not decide whether the result is normal.
How far apart should height or length measurements be?
AAP guidance says the earlier height or length is ideally at least 6 months before the later one. This page warns when fewer than 6 complete calendar months have passed but still shows the arithmetic.
Why can a short interval be misleading?
Small differences in posture, equipment, time, or technique can be large compared with the true change over a short interval. Annualizing magnifies that difference and does not predict the next year.
Does this tell me whether my child’s growth is normal?
No. It does not apply normal or abnormal thresholds. Clinical interpretation may consider age, puberty, health history, accurate repeated measurements, and the appropriate growth reference.
What if the later height or length is lower?
The decrease remains visible. Recheck dates, units, posture, shoes, equipment, and whether both measurements used the same lying-down or standing method. The calculator does not infer a cause.
What if the later weight is lower?
First recheck dates, units, clothing, food or drink timing, the scale, and measurement conditions. It may be a real recorded change, but this calculator does not label a cause or diagnosis.
Can I compare lying-down length with standing height?
No. Use the same method for both dates. The CDC SAS contract adds 0.8 cm to standing height measured before 24 months and subtracts 0.8 cm from recumbent length measured at 24 months or older. This calculator performs neither conversion. Do not adjust a clinical record yourself; if the method changed, an appropriate healthcare professional should decide how to handle it.
Is growth velocity the same as a percentile?
No. A velocity is a rate between two observations. A percentile compares a measurement or interval with a defined reference. This calculator provides no velocity percentile.
Does this calculator use WHO infant velocity standards?
No. WHO publishes separate weight- and length-velocity standards for specific early-childhood intervals. This page does not load those tables or calculate a WHO velocity z-score or percentile.
Does this site save the measurements?
Calculator inputs are processed in your browser and are not saved as a child health record or sent to an external calculation service.