Standard Atmospheres to Megapascals (atm to MPa)

1 standard atmosphere equals 0.101325 megapascals exactly.

1 standard atmosphere = 0.101325 megapascals

How to convert standard atmospheres to megapascals

To convert standard atmospheres to megapascals, multiply the number of standard atmospheres by 0.101325. This factor is exact. To go the other way, multiply megapascals by 9.869232667 (rounded).

megapascals = standard atmospheres × 0.101325

Example: 10 standard atmospheres = 1.01325 megapascals.

About these units

Standard Atmosphere (atm)

Metric (SI)Current unit

Exactly 101,325 pascals, the average pressure of the atmosphere at sea level.

A column of mercury about 76 cm tall was Torricelli's measure of the air, and the standard atmosphere began as exactly that: the pressure of 760 mm of mercury at 0 degrees Celsius under standard gravity. It was used as a reference for physical and chemical properties, and the Celsius scale set 100 degrees as the boiling point of water at that pressure.

In 1954 the 10th CGPM confirmed the standard atmosphere as exactly 1,013,250 dynes per square centimeter, which is 101,325 pascals, a definition that no longer depends on the properties of any substance.

In practice one atmosphere is about 1.01325 bar, 760 mmHg, 14.696 psi or 29.92 inHg, and roughly the pressure of 10.33 meters of water. Chemistry splits on it: until 1982 standard temperature and pressure used 1 atm, but that year IUPAC recommended a standard pressure of exactly 100 kPa instead.

1 standard atmosphere = 101,325 pascals (exactly).

Sources: Wikipedia: Standard atmosphere (unit); Wikipedia: Atmospheric pressure; Wikipedia: Evangelista Torricelli

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

Related conversions

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