BYTETOOLS

Blood Pressure Calculator

Classify a blood pressure reading against the 2017 ACC/AHA categories and calculate pulse pressure and mean arterial pressure, with an averaging mode.

Your reading

Classification

120/80mmHg

Stage 1 hypertension2017 ACC/AHA category

130–139 systolic, or 80–89 diastolic.

120 mmHg
Systolic
80 mmHg
Diastolic
40 mmHg
Pulse pressure
93 mmHg
Mean arterial pressure

Derived values

  • Pulse pressure = systolic − diastolic = 120 − 80 = 40 mmHg. Roughly 40 mmHg is typical; a persistently wide pulse pressure often reflects stiffer arteries.
  • Mean arterial pressure = diastolic + pulse pressure ÷ 3 = 80 + 40/3 = 93.3 mmHg. This is the standard bedside approximation of average pressure over the cardiac cycle; it assumes a resting heart rate and gets less accurate when the pulse is fast.
  • Average pulse 70 bpm across the readings that had one entered.

2017 ACC/AHA categories

CategorySystolic (mmHg)Diastolic (mmHg)
NormalBelow 120and below 80
Elevated120–129and below 80
Stage 1 hypertension130–139or 80–89
Stage 2 hypertension140 or aboveor 90 or above
Hypertensive crisisAbove 180and/or above 120

Classification uses whichever of the two numbers falls in the higher category. These are the 2017 American College of Cardiology / American Heart Association adult thresholds. Other bodies differ — the European Society of Cardiology and NICE in the UK still set the hypertension threshold at 140/90 in the clinic, so a reading labelled “Stage 1” here would be called high-normal there.

This tool categorises numbers you type in. It does not diagnose hypertension, and it is not medical advice. A diagnosis is never made from one reading: it needs several readings on separate days, taken correctly, and usually home or 24-hour ambulatory monitoring. Cuff size, arm position, a full bladder, caffeine, talking and white-coat effect can each move a reading by 10 mmHg or more. Take any result you are unsure about to a doctor or pharmacist, and never start, stop or change a medication based on a web calculator.

What is the Blood Pressure Calculator?

A blood pressure calculator places a systolic/diastolic reading into a guideline category and derives pulse pressure (systolic − diastolic) and mean arterial pressure (diastolic + pulse pressure ÷ 3). A reading of 120/80 gives a pulse pressure of 40 and a MAP of about 93 mmHg.

  • 2017 ACC/AHA categories including the hypertensive-crisis warning
  • Pulse pressure and mean arterial pressure with the formulas shown
  • Averaging mode for up to 20 readings, with per-reading categories
  • mmHg and kilopascal output
  • Full category threshold table for reference
  • Runs completely offline — readings never leave your device

How to use the Blood Pressure Calculator

  1. 1

    Choose whether you are entering one reading or averaging several.

  2. 2

    Type in the systolic (higher) and diastolic (lower) numbers for each reading.

  3. 3

    Add the pulse if your monitor showed one — it is optional.

  4. 4

    Read the ACC/AHA category, pulse pressure and mean arterial pressure.

  5. 5

    Switch the display to kPa if that is the unit you need.

About the Blood Pressure Calculator

The ByteTools Blood Pressure Calculator takes a reading you have already measured and tells you which category it falls into under the 2017 American College of Cardiology / American Heart Association guideline, from normal through elevated and stage 1 and 2 hypertension to hypertensive crisis. It also calculates pulse pressure and mean arterial pressure, the two derived numbers clinicians look at most often.

Because a single reading means very little, there is an averaging mode: add as many readings as you like and the tool averages them, classifies the average, and also shows the category each individual reading would fall into. Results can be displayed in mmHg or kilopascals, and the full ACC/AHA threshold table is included so you can see exactly where the boundaries sit.

Everything is calculated in your browser and no readings are uploaded or stored. This tool categorises numbers — it does not diagnose hypertension and it is not medical advice. A diagnosis needs several correctly taken readings on separate days, usually with home or ambulatory monitoring, so take anything that concerns you to a doctor or pharmacist rather than acting on it yourself.

Frequently asked questions

What is a normal blood pressure reading?

Under the 2017 ACC/AHA guideline, normal means a systolic below 120 and a diastolic below 80 at the same time. 120–129 over under 80 is called elevated, 130–139 or 80–89 is stage 1 hypertension, and 140 or above or 90 or above is stage 2.

How do you calculate mean arterial pressure?

MAP is diastolic pressure plus one third of the pulse pressure: MAP = DBP + (SBP − DBP) ÷ 3. For a 120/80 reading that is 80 + 40/3, which comes to about 93 mmHg. It approximates the average pressure over one cardiac cycle, weighting diastole more heavily because the heart spends longer in it.

How accurate is classifying a single reading?

Not accurate enough to act on. Blood pressure varies substantially minute to minute and across the day, and cuff size, arm position, a full bladder, caffeine, talking during measurement and white-coat effect can each shift a reading by 10 mmHg or more. That is why guidelines require several readings on separate occasions, and often 24-hour ambulatory monitoring, before making a diagnosis.

What is a hypertensive crisis?

A reading above 180 systolic and/or above 120 diastolic. The ACC/AHA advises resting five minutes and re-measuring; if it stays that high you need medical attention promptly, and immediately if there is also chest pain, breathlessness, weakness, vision change or difficulty speaking.

Why do UK and European guidelines give a different answer?

Because they draw the lines in different places. The 2017 ACC/AHA guideline lowered the American hypertension threshold to 130/80, while the European Society of Cardiology and NICE in the UK still use 140/90 for a clinic diagnosis. A reading labelled stage 1 here would be described as high-normal under those guidelines.

What does a wide pulse pressure mean?

Pulse pressure is the gap between the two numbers, typically around 40 mmHg. A persistently wide gap often reflects stiffer large arteries, which becomes more common with age, while a very narrow one can appear when stroke volume is low. It is one signal among many and is not interpretable on its own — that is a conversation for your clinician.

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