Pascal (Pa)

Metric (SI)Current unit

The SI unit of pressure: one newton per square meter. A very small unit; atmospheric pressure is about 101,325 Pa.

The pascal is the reference unit for pressure on this site.

About the pascal

Blaise Pascal never saw a pascal, because the name was adopted by the 14th CGPM in 1971 for the newton per square meter. He did, however, earn the honor. In 1647 he published experiments on the vacuum, and on 19 September 1648 his brother-in-law Florin Périer carried a mercury barometer up the Puy de Dôme near Clermont, where the column stood at about 23 inches against about 26 at the base. Pascal had reasoned that air pressure should fall with altitude, and the result confirmed it.

One pascal is a tiny pressure, so the unit is mostly met with prefixes. Standard atmospheric pressure is 101,325 Pa, a typical sea-level reading is about 1,013 hPa, and the threshold of hearing in air is taken as a reference pressure of 20 micropascals. Building airtightness tests, in contrast, are run at 50 Pa.

Pascal is also remembered for hydrostatics, where he showed that pressure depends on height difference rather than the weight of the fluid, and for the hydraulic press.

Sources: Wikipedia: Pascal (unit); Wikipedia: Blaise Pascal

Pascal conversion chart

1 pascal expressed in every other pressure unit:

More Metric (SI) units

• kilopascal (pressure)
• hectopascal (pressure)
• megapascal (pressure)
• gigapascal (pressure)
• bar (pressure)
• millibar (pressure)
• standard atmosphere (pressure)
• meter (length)
• kilometer (length)
• centimeter (length)
• millimeter (length)
• micrometer (length)
• nanometer (length)
• picometer (length)
• decimeter (length)
• hectometer (length)

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