Millimeters of Mercury to Kilopascals (mmHg to kPa)

Blood pressure is measured in millimeters of mercury almost everywhere, even in countries that use SI units for everything else, and US laboratories report arterial blood gases in mmHg too. Hospitals in the UK and several other European countries give blood gas results in kilopascals instead, so students, clinicians and patients reading results from both systems need the conversion.

The millimeter of mercury used here is the conventional one, exactly 133.322387415 pascals, defined from a standard mercury density and standard gravity rather than a real column. The torr, used in vacuum work, is very nearly the same size but is defined as 1/760 of a standard atmosphere; the two differ by about one part in seven million.

How to use this tool

1. Type a value in the Millimeter of Mercury box to see it in kilopascals, or type in the Kilopascal box to convert the other way.
2. Press ⇄ to swap the two units, or Load example for a typical value.
3. Check the charts below for common values; for other units, open the Pressure converter.

Formula

Kilopascal (kPa) = Millimeter of Mercury (mmHg) × 0.133322387415

Millimeter of Mercury (mmHg) = Kilopascal (kPa) × 7.50061575846

Both factors come from exact definitions: 1 kilopascal = 7.50061575846 millimeters of mercury and 1 millimeter of mercury = 0.133322387415 kilopascals (shown to 12 significant digits).

Example

Two conversions worked with the same factors the converter uses:

120 mmHg × 0.133322387415 ≈ 15.9987 kPa

5.3 kPa × 7.50061575846 ≈ 39.7533 mmHg

Millimeter of Mercury to Kilopascal chart

Common values from millimeters of mercury to kilopascals, rounded to four decimal places.

Kilopascal to Millimeter of Mercury chart

The reverse direction for values people often look up.

Clinical and reference values in mmHg

Quick mental estimate

Divide by 7.5: 120 mmHg → 16 kPa, and 40 mmHg → 5.3 kPa. A kilopascal is 7.50062 mmHg, so dividing by 7.5 is off by less than 0.01%.

Use the converter or the charts when the exact figure matters.

The two units

Millimeter of Mercury (mmHg): The conventional millimeter of mercury used here is exactly 133.322387415 Pa: 1 mm of a notional liquid of density 13,595.1 kg/m³ under standard gravity. The pressure-context shorthand mm selects mmHg, not an unspecified liquid column.

Kilopascal (kPa): A kilopascal (kPa) is 1,000 pascals. It is used for tire pressures, weather and engineering in metric countries; standard sea-level air pressure is 101.325 kPa.