How this calculator works
This page implements Appendix B and Table B-1 of the NHLBI Fourth Report (2004). CDC 2000 stature LMS rows supply the sex- and age-specific height z-score, with linear interpolation between reference ages. The blood pressure equations use age in years and height z-score. These are historical reference percentiles, not the 2017 AAP normal-weight reference tables and not a current hypertension classification. A diagnosis requires properly measured repeated readings and clinical assessment. Children under 2 are excluded because this method uses standing stature data starting at 24 months. The result is an estimate for information only and is not medical advice.
Formula
Height z = ((height/M)^L - 1)/(L S), or ln(height/M)/S when L = 0. Expected BP = alpha + sum(beta_j × (age-10)^j) + sum(gamma_k × heightZ^k), j and k = 1 to 4. BP z = (measured BP - expected BP)/sigma. Percentile = normal CDF(BP z).
Worked example
For a 10-year-old boy at the CDC median height, SBP 102.19768 mmHg has z = 0 and is at the 50th percentile. For a girl at the same age and her median height, DBP 60.50510 mmHg is at the 50th percentile.
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Frequently asked questions
Is this the current AAP diagnostic table?
No. It deliberately reports the fully published 2004 NHLBI reference equations. The 2017 AAP guideline changed the reference population and classification; these results must not be substituted for that guideline.
Why is height needed?
Expected blood pressure changes with body size as well as age and sex. CDC stature data determine the height adjustment in this model.
Does a single high percentile diagnose hypertension?
No. Cuff fit, technique, repeated measurements and the clinical setting matter. This page does not make a diagnosis.