How this instrument works
This calculator implements the simplified screening formulas published by Hassanzadeh Rad, Kamalpour, Badeli, and colleagues in the Iranian Journal of Kidney Diseases in 2023. The authors derived simple, memorable equations for estimating the blood pressure thresholds used to screen for elevated blood pressure and hypertension in children, and validated those equations against the full height-percentile-based lookup tables in the 2017 American Academy of Pediatrics (AAP) Clinical Practice Guideline.
The 2017 AAP guideline itself defines elevated pediatric blood pressure using tables that combine age, sex, and height percentile — accurate, but cumbersome to use without a reference chart or calculator on hand. The Hassanzadeh Rad formulas collapse that lookup into two simple linear equations, one for the systolic threshold and one for the diastolic threshold, using only age and sex, so a threshold can be estimated at the bedside without consulting the full table.
This tool covers ages 1 through 12 only, the population the formulas were derived and validated for. From age 13 onward, the 2017 AAP guideline switches to the same fixed adult-style cutoffs used for adolescents and adults (120/80 mmHg), and this calculator does not compute those — it is scoped specifically to the younger pediatric range where age- and sex-based thresholds apply.
A flagged result here means the measured reading is at or above the estimated screening threshold for that child's age and sex — a reason to recheck the measurement and follow up with a pediatrician, not a diagnosis of hypertension. Diagnosing pediatric hypertension requires the full height-percentile tables and, typically, repeated measurements on separate occasions.
- Enter the child's age in whole years (this calculator is validated for ages 1 through 12 only).
- Set 'Sex is female' to Yes or No, since the screening thresholds differ slightly by sex.
- Enter the measured systolic blood pressure in mmHg from a blood pressure reading.
- Enter the measured diastolic blood pressure in mmHg from the same reading.
- Read the estimated screening SBP and DBP thresholds for the child's age and sex, and whether the measured systolic and diastolic readings are at or above each threshold.
Worked example — three children, three outcomes
A 6-year-old boy has a screening SBP threshold of 6 + 98 = 104 mmHg and a DBP threshold of 6×2 + 52 = 64 mmHg. A measured reading of 105/65 is at or above both thresholds, so both systolic and diastolic readings flag for follow-up with a pediatrician and a repeat measurement.
A 6-year-old girl has slightly higher thresholds, 6 + 99 = 105 mmHg systolic and 6×2 + 53 = 65 mmHg diastolic. A measured reading of 100/60 falls comfortably under both, so neither flags — the same numeric reading that flagged the boy above would not flag this girl, because the thresholds differ by sex.
A 10-year-old boy has a screening SBP threshold of 10 + 98 = 108 mmHg and a DBP threshold of 10×2 + 52 = 72 mmHg. A measured reading of 108/70 is exactly at the systolic threshold, so it flags, but 70 is under the diastolic threshold of 72, so the diastolic reading does not flag — illustrating that systolic and diastolic results can disagree on the same child.
Questions
Can I use this for a teenager or adult?
No. This calculator is scoped to ages 1 through 12, the population the underlying formulas were derived and validated for. From age 13 on, the 2017 AAP guideline applies the same fixed cutoffs used for adolescents and adults — 120/80 mmHg — and this calculator does not compute or apply those adult thresholds.
Does a flagged result mean my child has hypertension?
No. A flagged result means the measured reading is at or above the estimated screening threshold for that age and sex — a signal to recheck the measurement and follow up with a pediatrician, not a diagnosis. Diagnosing pediatric hypertension under the 2017 AAP guideline requires the full height-percentile tables and, typically, elevated readings confirmed on repeated occasions.
Why do these simplified formulas leave out height?
The full 2017 AAP guideline tables incorporate height percentile along with age and sex. Hassanzadeh Rad and colleagues derived age-and-sex-only equations specifically as a quick screening approximation of those tables and validated the approximation's accuracy against the full guideline — it is designed for fast bedside screening, not as a replacement for the complete height-based tables when precision matters.
Why are the thresholds slightly different for girls and boys?
The underlying 2017 AAP guideline tables show sex-specific blood pressure distributions in children, and the Hassanzadeh Rad formulas preserve that by adding 99 (systolic) or 53 (diastolic times two) for girls versus 98 and 52 for boys, keeping the simplified equations consistent with the full guideline's sex-specific cutoffs.
What inputs does the calculator need?
The child's age in whole years (1 to 12), sex, and a measured systolic and diastolic blood pressure reading in mmHg. The calculator returns the estimated screening thresholds for that age and sex and flags whether each measured value is at or above its threshold.
Is this a substitute for a pediatrician's evaluation?
No. It's a screening reference tool for parents and clinicians to quickly check a reading against an approximate threshold. It doesn't replace a clinical evaluation, the full height-percentile AAP tables, or repeated-measurement confirmation, all of which a pediatrician would use before making any diagnosis.
References
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.