Pediatric Blood Pressure Calculator
Enter the child's age, sex, height, and blood pressure reading to get the systolic and diastolic percentiles and the 2017 American Academy of Pediatrics classification. The tool uses normative tables derived from normal-weight children and correctly switches to absolute adult thresholds for adolescents aged 13 and older. Results update as you type.
How children's blood pressure is classified
Unlike adults, where a single cut-off applies to everyone, normal blood pressure in children and adolescents depends on age, sex, and height. Taller children naturally have somewhat higher blood pressure, so the 2017 American Academy of Pediatrics (AAP) guideline provides sex- and height-specific percentile tables for ages 1 through 17. A reading below the 90th percentile for a child's particular age, sex, and height is considered normal. A reading between the 90th and 95th percentile (or at or above 120/80 mmHg, whichever is lower) is labelled elevated blood pressure, formerly called pre-hypertension. Stage 1 hypertension spans from the 95th percentile up to the 95th percentile plus 12 mmHg. Stage 2 hypertension is anything at or above the 95th percentile plus 12 mmHg, or at or above 140/90 mmHg. For adolescents aged 13 and older, the guideline transitions to adult-style absolute thresholds, aligning with the 2017 AHA/ACC adult guidelines.
How this calculator works
Select the child's biological sex, enter their age in years (whole numbers or halves), their height, and the systolic and diastolic blood pressure values from the current reading. The tool first converts height into a height percentile using CDC growth-reference medians and standard deviations, then selects the matching column in the AAP 2017 normative tables. It reads the 50th, 90th, 95th, and 99th percentile thresholds for systolic and diastolic BP separately, interpolates where the measured values fall, and applies the AAP 2017 classification rules. The resulting percentile, reference thresholds, and category are shown together so you can see exactly how the result was reached. This tool is a clinical support aid and cannot replace a full clinical assessment by a qualified healthcare professional.
Why height matters for blood pressure in children
Blood pressure tends to rise as children grow taller, independently of age. A six-year-old who is in the 95th percentile for height will have a naturally higher blood pressure than a six-year-old at the 5th height percentile, and the same raw reading of, say, 108 mmHg systolic could be normal for the taller child but elevated for the shorter one. The AAP 2017 normative tables account for this by providing separate thresholds for seven height percentile columns: the 5th, 10th, 25th, 50th, 75th, 90th, and 95th. The 2017 AAP guideline also revised the normative data by excluding overweight and obese children from the reference population, which lowered the typical values by 2 to 3 mmHg compared with the older 2004 NHLBI fourth report tables.
Interpreting the result and next steps
Blood pressure should never be diagnosed from a single reading. The AAP recommends confirming any elevated or hypertensive reading on at least two separate visits before making a diagnosis. Factors such as the child being anxious, having recently exercised, or the cuff being the wrong size can all raise a reading. White-coat hypertension (elevated readings only in clinical settings) is common in children. If blood pressure is persistently elevated, the workup typically starts with lifestyle review, diet, and weight assessment, and then moves on to ruling out secondary causes such as kidney disease, coarctation of the aorta, and endocrine disorders, particularly for younger children where primary hypertension is less common.
AAP 2017 Blood Pressure Classification (Ages 1-17)
| Category | Ages 1-12 threshold | Ages 13-17 threshold | Action |
|---|---|---|---|
| Normal | < 90th percentile | < 120/80 mmHg | Routine annual screening |
| Elevated BP | 90th to < 95th pctile, or >= 120/80 (lower) | 120-129 / < 80 mmHg | Recheck in 6 months; lifestyle changes |
| Stage 1 Hypertension | 95th to < 95th pctile + 12 mmHg | 130-139 / 80-89 mmHg | Recheck in 1-2 weeks; evaluate |
| Stage 2 Hypertension | >= 95th pctile + 12 mmHg, or >= 140/90 | >= 140/90 mmHg | Prompt evaluation; consider referral |
Based on the 2017 American Academy of Pediatrics Clinical Practice Guideline. For ages 1-12, thresholds are age-, sex-, and height-specific. For ages 13+, adult absolute thresholds apply.
Frequently asked questions
What is a normal blood pressure for a child?
Normal pediatric blood pressure is defined as below the 90th percentile for the child's specific age, sex, and height. Because these thresholds vary considerably with growth, there is no single universal number. For example, the 90th percentile systolic threshold for an average-height 5-year-old girl is around 103 mmHg, while for an average-height 15-year-old boy it is around 125 mmHg. For adolescents 13 and older, the AAP guideline uses adult-style cut-offs: normal is below 120/80 mmHg.
Why does height affect the blood pressure classification?
Taller children have larger blood vessels and hearts, which naturally supports somewhat higher pressures. The AAP 2017 normative tables account for this relationship by providing separate reference thresholds for seven height percentile columns (5th through 95th). Ignoring height can lead to incorrectly labelling a tall child as hypertensive or missing elevated blood pressure in a short child.
What is the difference between the 2004 NHLBI and 2017 AAP tables?
The 2004 NHLBI fourth report included overweight and obese children in the reference population. Because excess weight raises blood pressure, this inflated the "normal" thresholds. The 2017 AAP guideline reanalyzed the same dataset excluding children with a BMI at or above the 85th percentile, which lowered the thresholds by 2 to 3 mmHg for children aged 12 and under. This means that more children may now be classified as having elevated or hypertensive blood pressure compared with the older tables, even if their actual readings have not changed.
Can a single blood pressure reading diagnose hypertension?
No. The AAP recommends confirming elevated or hypertensive readings on at least two separate visits before making a diagnosis. Blood pressure varies considerably with activity, anxiety, and even time of day. Children are especially prone to white-coat hypertension, where readings are elevated in clinical settings but normal elsewhere. If repeated clinic readings are borderline, ambulatory blood pressure monitoring over 24 hours can provide a more reliable picture.
What causes high blood pressure in children?
In younger children and those with very high blood pressure, a secondary cause is often found. Common secondary causes include chronic kidney disease, renovascular disease, coarctation of the aorta, primary hyperaldosteronism, and thyroid disorders. In older children and adolescents, especially those with overweight or obesity, primary (essential) hypertension is more common and is linked to family history, a high-sodium diet, physical inactivity, and stress. The age and severity of hypertension guide how aggressively secondary causes need to be investigated.
How do I measure blood pressure accurately in a child?
Use the correct cuff size - the inflatable bladder should encircle 80 to 100 percent of the upper arm. A cuff that is too small will give falsely high readings. The child should sit quietly for at least 3 to 5 minutes before the measurement, with feet flat on the floor and the arm supported at heart level. Take the reading in the right arm by default. Measure two or three times and average the readings. Oscillometric (electronic) devices are acceptable for screening but should be confirmed with auscultatory measurements if elevated.
Sources
- Flynn JT, et al. Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents. Pediatrics. 2017;140(3):e20171904. American Academy of Pediatrics.
- National Heart, Lung, and Blood Institute. The Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents. Pediatrics. 2004;114(2):555-576.