How this calculator works
The millimetre of mercury is a legacy pressure unit based on the height of a mercury column. The conventional value used here is 133.322387415 Pa at 0 °C, a fixed definition rather than a measurement made each time. One kilopascal is 1,000 Pa, so a reading in kilopascals divides by 0.133322387415 to become mmHg. Medicine still reports blood pressure in mmHg even where other pressures use kilopascals.
Formula
mmHg = kPa x 1000 / 133.322387415. kPa = mmHg x 0.133322387415. Because 1 mmHg is 133.322387415 Pa, 1 kPa is about 7.50062 mmHg.
Worked example
16 kPa = 120.010 mmHg, close to a systolic reading of 120. 10 kPa = 75.0062 mmHg. 101.325 kPa = 759.9999 mmHg, which is just under 760 because mmHg and the torr are slightly different. 1 kPa = 7.50062 mmHg.
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Frequently asked questions
Is mmHg exactly the same as torr?
No. The torr is defined as 1/760 of a standard atmosphere, which is 133.322368421 Pa. The conventional millimetre of mercury is 133.322387415 Pa. The difference is about one part in ten million and does not matter for ordinary measurements.
Why is blood pressure still given in mmHg?
The mercury manometer was the standard clinical instrument for generations, and the unit remains on monitors and in guidelines. Modern digital devices measure electronically but still display the result in mmHg.
Can I convert a blood pressure reading with this page?
Yes, it converts the pressure value, for example 16 kPa to about 120 mmHg. It does not interpret, diagnose or recommend a blood pressure. Ask a clinician about what a reading means for you.
Why is the factor 133.322 and not 133.3?
The conventional definition uses the density of mercury at 0 °C and standard gravity, giving 133.322387415 Pa. Rounding it to 133.3 Pa would introduce an error of about one part in 5,900.