Blood Pressure Converter
Convert blood pressure readings between mmHg, kPa, and cmH2O instantly.
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Type in any field — the others update instantly.
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Blood pressure is traditionally measured in millimeters of mercury (mmHg), a unit left over from the mercury-column gauges doctors relied on for more than a century. The number literally meant how far the pressure could push mercury up a tube. Most monitors are digital now, but the unit stuck.
Conversion factors:
- 1 mmHg = 0.1333 kPa
- 1 kPa = 7.5006 mmHg
- 1 mmHg = 1.3595 cmH₂O
A reading always comes as two numbers, written as systolic over diastolic. Systolic is the higher figure, the pressure as the heart beats; diastolic is the lower, the pressure while the heart rests between beats.
Typical ranges (systolic/diastolic):
- Normal: around 120/80 mmHg (about 16.0/10.7 kPa)
- Elevated: 120–129 systolic, under 80 diastolic
- High, stage 1: 130–139 / 80–89 mmHg
- High, stage 2: 140+ / 90+ mmHg
Most of the world reports blood pressure in mmHg, but a handful of countries and many research settings use kilopascals, which is the usual reason to convert. The figures look alarmingly different at first: a normal 120/80 in mmHg is roughly 16/11 in kPa, so the smaller numbers aren’t a cause for worry, they describe the same pressure. This is general information, not medical advice.
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This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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