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Multiple conversions
To convert from hectopascal (hPa) to pascal (Pa), use the following formula:
pascal (Pa)
= 110 × 1000× hectopascal (hPa)
= 100× hectopascal (hPa)
To convert from hectopascal (hPa) to kilopascal (kPa), use the following formula:
kilopascal (kPa)
= 110× hectopascal (hPa)
= 0.1× hectopascal (hPa)
To convert from hectopascal (hPa) to megapascal (MPa), use the following formula:
megapascal (MPa)
= 110 × 11000× hectopascal (hPa)
= 1104× hectopascal (hPa)
= 10-4× hectopascal (hPa)
To convert from hectopascal (hPa) to millibar (mbar), use the following formula:
millibar (mbar)
= 110 × 10× hectopascal (hPa)
= 1× hectopascal (hPa)
To convert from hectopascal (hPa) to bar (bar), use the following formula:
bar (bar)
= 110 × 1100× hectopascal (hPa)
= 11000× hectopascal (hPa)
= 0.001× hectopascal (hPa)
To convert from hectopascal (hPa) to torr (torr), use the following formula:
torr (torr)
= 110 × 760000101325× hectopascal (hPa)
= 0.7500616827041697508× hectopascal (hPa)
To convert from hectopascal (hPa) to meter of water @ 4°C (mH2O), use the following formula:
meter of water @ 4°C (mH2O)
= 110 × 19.80665× hectopascal (hPa)
= 0.010197162129779282426× hectopascal (hPa)
To convert from hectopascal (hPa) to millimeter of mercury (mmHg), use the following formula:
millimeter of mercury (mmHg)
= 110 × 10.133322× hectopascal (hPa)
= 0.7500637554192106329× hectopascal (hPa)
To convert from hectopascal (hPa) to pound per square inch (psi), use the following formula:
pound per square inch (psi)
= 110 × 0.00014503768078 × 1000× hectopascal (hPa)
= 100 × 0.00014503768078× hectopascal (hPa)
= 0.014503768078× hectopascal (hPa)
With 0.00014503768078 is the ratio between the base units kilopound per square inch (ksi) and kilopascal (kPa).
To convert from hectopascal (hPa) to kilopound per square inch (ksi), use the following formula:
kilopound per square inch (ksi)
= 110 × 0.00014503768078× hectopascal (hPa)
= 0.000014503768078× hectopascal (hPa)
With 0.00014503768078 is the ratio between the base units kilopound per square inch (ksi) and kilopascal (kPa).
To convert a pressure from hectopascals (hPa) to inches of mercury (inHg), multiply by 0.02953.
The factor follows from the conventional inch of mercury (3,386.39 Pa) and the hectopascal (exactly 100 Pa): 100 ÷ 3,386.39 = 0.029530. The touchstone every meteorologist knows: 1,013.25 hPa = 29.92 inHg, the standard atmosphere in both dialects.
A hurricane advisory reports a central pressure of 920 hPa, and a US audience expects inches of mercury:
Divide by 0.02953 to convert the other way: a home barometer showing 30.10 inHg is reading 1,019.3 hPa.
| hPa | inHg |
|---|---|
| 870 | 25.69 |
| 920 | 27.17 |
| 980 | 28.94 |
| 1,013.25 | 29.92 |
| 1,030 | 30.42 |
| 1,050 | 31.01 |
The hectopascal is the world's meteorological standard — chosen because 1 hPa equals exactly 1 millibar, letting decades of weather records carry over unchanged when the SI name was adopted. The United States is the major holdout: public forecasts, home barometers and aviation altimeter settings (with Canada) still use inches of mercury. The same physical reading therefore circulates in two dialects — a METAR from Frankfurt says Q1013 (hPa) while one from Chicago says A2992 (inHg), both describing a standard day. Anyone comparing international weather data, tracking Atlantic hurricanes (advisories quote hPa/mb even for US audiences), or flying between the two systems performs this conversion routinely. The extreme ends of the table above are not decorative: 870 hPa is the lowest sea-level pressure ever measured (Typhoon Tip, 1979) and values above 1,050 hPa occur in strong Siberian winter highs — real barometric readings span that whole range.
A hectopascal (hPa) is a metric unit used to measure pressure.
You will most commonly see it in weather reports to describe atmospheric pressure (also known as barometric pressure).
If you've seen millibars (mbar) on older weather maps, the hectopascal is its modern replacement.
The switch was simple for meteorologists because the units are exactly the same (1 hPa = 1 mbar).
The hectopascal is now the international standard for measuring atmospheric pressure, making weather data consistent worldwide.
The conversion is in the name. The prefix "hecto-" means 100. This makes the math simple:
Just as "hecto-" means 100, "kilo-" means 1,000. This defines their relationship: