Hectopascals to Pascals (hPa to Pa)

1 hectopascal equals 100 pascals exactly.

1 hectopascal = 100 pascals

How to convert hectopascals to pascals

To convert hectopascals to pascals, multiply the number of hectopascals by 100. This factor is exact. To go the other way, multiply pascals by 0.01.

pascals = hectopascals × 100

Example: 10 hectopascals = 1,000 pascals.

About these units

Hectopascal (hPa)

Metric (SI)Current unit

100 pascals, equal to one millibar. The standard unit in weather forecasts and barometers.

Weather forecasters rarely think in pascals, and the hectopascal exists largely to avoid changing their numbers. When SI arrived, meteorologists generally switched from the millibar to the hectopascal, which equals exactly 100 Pa and exactly one millibar, so existing readings carried over unchanged. Observations are typically reported in hPa, following the World Meteorological Organization recommendation, though many scientific fields dislike the hecto prefix because they prefer steps of 1,000.

A typical sea-level reading is about 1,013 hPa. The lowest non-tornadic pressure ever measured was 870 hPa, in Typhoon Tip on 12 October 1979, and the highest sea-level pressure, 1,084.8 hPa, came at Tosontsengel, Mongolia, on 19 December 2001, at a station above 750 meters. At low altitudes, pressure drops about 12 hPa for every 100 meters you climb.

Aviation weather reports, such as the QNH in a METAR, use hectopascals or millibars in most countries, while the US, Canada and Japan quote altimeter settings in inches of mercury.

1 hectopascal = 100 pascals (exactly).

Sources: Wikipedia: Hectopascal; Wikipedia: Atmospheric pressure; Wikipedia: Pascal (unit)

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.

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.

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

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

Related conversions

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