Millimeters Of Mercury to Megapascals (mmHg to MPa)

1 millimeter of mercury equals 0.0001333223874 megapascals (rounded).

1 millimeter of mercury = 0.0001333223874 megapascals

How to convert millimeters of mercury to megapascals

To convert millimeters of mercury to megapascals, multiply the number of millimeters of mercury by 0.0001333223874. The factor is rounded to 10 significant digits. To go the other way, multiply megapascals by 7,500.615758 (rounded).

megapascals = millimeters of mercury × 0.0001333223874

Example: 10 millimeters of mercury = 0.001333223874 megapascals.

About these units

Millimeter Of Mercury (mmHg)

ScientificCurrent unit

About 133.322 pascals, the pressure from a 1 mm column of mercury. Blood pressure is still reported in mmHg.

Where the torr honors a person, the millimeter of mercury describes a gauge. It is a manometric unit: originally the pressure from a mercury column 1 mm tall, which means it depends on an assumed fluid density and on gravity. Mercury manometers were among the first accurate pressure gauges, and 17th-century experiments by Torricelli and then Pascal, whose mercury stood at about 23 inches on a mountaintop against about 26 at its base, showed that air has weight and that pressure drops with altitude.

To remove the ambiguity, mmHg is now fixed at exactly 133.322387415 Pa, using a conventional mercury density of 13,595.1 kg per cubic meter and standard gravity. The torr, defined as one 760th of a standard atmosphere, differs from it by only about 0.000015 percent.

Mercury is toxic and its readings vary with temperature and local gravity, so mercury gauges are now used less, and the unit's use is discouraged. Medicine nonetheless keeps it, especially for blood pressure, which is reported relative to atmospheric pressure, and hypertension guidelines in the US and Europe still use it.

1 millimeter of mercury = 133.3223874 pascals (approximately).

Sources: Wikipedia: Millimetre of mercury; Wikipedia: Torr; Wikipedia: Blaise Pascal

Megapascal (MPa)

Metric (SI)Current unit

One million pascals. Used for material strength and hydraulic pressure.

Engineers reach for the megapascal because the pascal is far too small for solid materials. It is the preferred unit in engineering for stiffness and for tensile or compressive strength, and stiffness figures go on to gigapascals: aluminium is given as 69 GPa, structural steel as 200 GPa, and diamond as 1,220 GPa.

Fluid systems live in the same range. One megapascal is 10 bar, so scuba tanks filled to about 200 bar sit at 20 MPa, and fixed industrial hydraulic machinery commonly working at around 300 bar runs at about 30 MPa. A kilobar, used in experimental petrology, is 100 MPa.

For comparison with units from the pounds-and-inches world, one psi is about 6.895 kPa, so a megapascal is about 145 psi.

1 megapascal = 1,000,000 pascals (exactly).

Sources: Wikipedia: Pascal (unit); Wikipedia: Bar (unit); Wikipedia: Pounds per square inch

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