Bone Age Calculator
Bone age is read by a radiologist from a hand-and-wrist X-ray, usually against the Greulich and Pyle atlas. This tool takes the bone age from the report and compares it with your child's exact age on the X-ray date. It does not read X-rays and no longer predicts adult height.
Before you start
Method : Your child's exact age on the X-ray date compared with the bone age written on the report. Nothing is predicted.
Validation : Date arithmetic uses the site's tested calendar rules. No clinical interpretation is given.
Review : not reviewed by a qualified clinician. Educational only — not a diagnosis or a medical test.
For children and teenagers with a bone age report. This tool cannot read an X-ray.
Your answers stay in this browser tab; nothing is sent or stored.
Enter the dates and the reported bone age.
How to Use This Calculator
- Enter the date of birth and the X-ray date (leave empty for today).
- Enter the bone age from the report.
- Press Compare.
Methodology & assumptions
Exact age on the X-ray date is counted in completed calendar months using the site's date rules (short months clamp to their last day). Difference = reported bone age in months − exact age in months. No "normal/advanced/delayed" label is given, because the cut-off depends on the atlas, age and sex.
Worked examples
Born 2015-03-10, X-ray 2026-09-20, bone age 13 y 0 m: exact age 11 y 6 m (138 months); bone age 156 months; difference +18 months (bone age ahead).
Born 2018-01-31, X-ray 2026-02-28, bone age 7 y 6 m: exact age 8 y 1 m (97 months — a month after Jan 31 is reached on Feb 28); difference −7 months.
Understanding your result
The difference is just arithmetic. Bone age readings themselves vary between readers by several months, and whether a difference matters depends on the child. Only the treating doctor can interpret it.
Sources & further reading
Frequently Asked Questions
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