Blood Pressure Category Checker
Enter one or more blood pressure readings to see the NHLBI category (normal, elevated, stage 1, stage 2 or hypertensive crisis), the average, mean arterial pressure and pulse pressure, plotted on a systolic-against-diastolic chart.
How to Use
- Enter a reading as systolic/diastolic, for example 128/82 (the top number first).
- To average several readings, put each on its own line or separate them with commas.
- Read the NHLBI category, the average reading, the mean arterial pressure and the pulse pressure.
- See where the reading sits on the chart, and check Show Work for how each reading was classed.
- Use a preset to see how the AND and OR rules of the table work.
Worked Example
One reading: 128/82. The systolic of 128 is below 130, but the diastolic of 82 is in 80–89, and Stage 1 is “130 to 139 systolic OR 80 to 89 diastolic”, so the reading is High Blood Pressure Stage 1. Mean arterial pressure = 82 + (128 − 82) ÷ 3 = 97.3 mm Hg; pulse pressure = 128 − 82 = 46 mm Hg.
Three home readings: 142/92, 138/88, 145/94. The average systolic is (142 + 138 + 145) ÷ 3 = 141.7 and the diastolic (92 + 88 + 94) ÷ 3 = 91.3, which round to 142/91: Stage 2, because the systolic is 140 or higher (and the diastolic 90 or higher).
The common mistake: looking only at the top number. At 128/92 the systolic alone would be Elevated, and at 120/80 it would look like the edge of Normal. But the table joins the stage rows with OR, so the diastolic counts on its own: 128/92 is Stage 2 (diastolic 90 or higher) and 120/80 is Stage 1 (diastolic 80–89). Normal needs both numbers below their limits.
Show Work
Formulas
Millimetres of Mercury and Today’s Categories
Blood pressure is still quoted in millimetres of mercury because the first practical cuff instruments read it off a column of mercury. The Italian physician Scipione Riva-Rocci introduced the inflatable arm cuff in 1896, and in 1905 the Russian surgeon Nikolai Korotkov described the sounds heard through a stethoscope as the cuff is let down, which mark the systolic and diastolic pressures. Electronic monitors now estimate the same two numbers.
The category table used here is the one the National Heart, Lung, and Blood Institute publishes: under 120/80 is normal, 130 systolic or 80 diastolic starts Stage 1, 140 or 90 starts Stage 2, and above 180/120 is a hypertensive crisis. These thresholds follow the 2017 American College of Cardiology and American Heart Association guideline, which moved the start of high blood pressure down from 140/90 to 130/80. For children younger than 13, the NHLBI notes that readings are instead compared with what is usual for children of the same age, sex and height.
About This Tool
This checker classes one reading, or the average of up to 50, with the NHLBI table’s AND and OR rules exactly as published, and shows which rule each reading met. It also gives mean arterial pressure and pulse pressure, and plots every reading and the average on a systolic-against-diastolic chart with the category regions. It is meant for adults; a category from readings you take yourself is information to share with your provider, not a diagnosis, which the NHLBI says needs two or more readings at separate appointments.
If any reading is above 180/120 mm Hg, the NHLBI says it is dangerously high and needs immediate medical attention. Everything runs in your browser; nothing you enter is sent anywhere.
For general information only — not medical advice. Talk to a doctor or other qualified professional about your own health.
Related tools: BMI Calculator, GFR Calculator, and Caffeine Intake & Half-Life Calculator.
Frequently Asked Questions
What do the two blood pressure numbers mean?
The top number, systolic, is the pressure while the heart pumps, when the pressure of blood against the vessels is highest. The bottom number, diastolic, is the pressure while the heart fills, when it is lowest. Both are in millimetres of mercury (mm Hg). In 128/82, the systolic is 128 and the diastolic 82.
What are the blood pressure categories?
The NHLBI table: Normal is less than 120 systolic AND less than 80 diastolic; Elevated is 120–129 AND less than 80; High Blood Pressure Stage 1 is 130–139 OR 80–89; Stage 2 is 140 or higher OR 90 or higher; Hypertensive Crisis is higher than 180 OR higher than 120, and the NHLBI says to contact your provider immediately. With OR, either number alone is enough, so 128/92 is Stage 2.
Is 120/80 a normal blood pressure?
Not by the NHLBI table. Normal needs a systolic below 120 and a diastolic below 80. At 120/80 the diastolic of 80 is in the Stage 1 range (80–89), so the reading is classed as High Blood Pressure Stage 1. The NHLBI says a healthy blood pressure for most adults is less than 120/80.
How should I take my blood pressure at home?
The NHLBI suggests no exercise, coffee or smoking for 30 minutes before, using the bathroom first, sitting quietly for at least 5 minutes with feet flat and not talking, and resting the bare arm on a table at heart level, with the right cuff size and an approved home device. Readings vary, so record several and average them; a diagnosis needs two or more readings at separate appointments.
What are mean arterial pressure and pulse pressure?
Mean arterial pressure is the average pressure over a heartbeat, usually estimated as diastolic + (systolic − diastolic) ÷ 3: for 120/80 that is 93.3 mm Hg, and for 128/82 it is 97.3. Pulse pressure is simply systolic − diastolic: 40 mm Hg for 120/80. This tool reports both but does not class them.
How do I use the Blood Pressure Category Checker?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Is it free? Does it work without internet?
Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.
Where does my data go?
Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.
Common Use Cases
A week of home readings
Readings of 142/92, 138/88 and 145/94 average 141.7/91.3, rounded to 142/91: High Blood Pressure Stage 2, even though the middle reading on its own is Stage 1.
One number in a higher row
At 128/92 the systolic alone would be Elevated, but the diastolic of 92 meets the Stage 2 rule (90 or higher), so the category is Stage 2.
Before an appointment
A log averaging 124/78 is Elevated (120–129 and below 80); the NHLBI advises talking to your provider when readings are consistently above 120/80.
Physiology homework
For 134/84, mean arterial pressure is 84 + 50 ÷ 3 = 100.7 mm Hg and pulse pressure is 50 mm Hg.
Knowing the crisis wording
A reading of 185/110 is a Hypertensive Crisis because the systolic is above 180; the NHLBI says readings above 180/120 need immediate medical attention.
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