Barometric Pressure Conversion
Convert barometric pressure between hPa, inHg, mmHg, atm, bar, psi, and more. Free online weather pressure converter for meteorology, aviation, and science.
About This Calculator
The Barometric Pressure Conversion Calculator converts atmospheric pressure between all major units used in meteorology, aviation, weather forecasting, and science. Barometric pressure — also called atmospheric pressure — is the force per unit area exerted by the weight of the atmosphere above a given point. It is a fundamental measurement in weather prediction, aviation altimeter settings, and scientific research.
This converter supports hectopascals (hPa, also known as millibars), inches of mercury (inHg), millimeters of mercury (mmHg), atmospheres (atm), bars, kilopascals (kPa), pascals (Pa), pounds per square inch (psi), torr, and megapascals (MPa). Enter any value and select its unit; the tool instantly calculates the equivalent pressure in every other unit. A bar chart compares all values visually.
Regional Notes: In the United States, barometric pressure is commonly reported in inches of mercury (inHg) by the National Weather Service. In Europe, Asia, and most other regions, hectopascals (hPa) are the standard unit for weather reports. The United Kingdom uses both hPa and mbar interchangeably. Aviation uses inHg for altimeter settings globally, but hPa is increasingly common in modern aircraft.
How to use: Enter a pressure value, select the unit from the dropdown, and click Convert. The results show the equivalent pressure in all units, plus a comparison chart. Standard sea-level pressure is 1013.25 hPa (29.92 inHg) — use this as a reference point for weather analysis.
Frequently Asked Questions
What is barometric pressure?
Barometric pressure, also called atmospheric pressure, is the pressure exerted by the weight of the air above a given point on Earth. It is measured using a barometer and is a key metric in weather forecasting. Standard sea-level pressure is 1013.25 hPa (29.92 inHg).
How do you convert barometric pressure from inHg to hPa?
To convert inches of mercury (inHg) to hectopascals (hPa), multiply the pressure in inHg by 33.8639. For example, standard sea-level pressure of 29.92 inHg equals 29.92 × 33.8639 = 1013.25 hPa.
What units are used for barometric pressure?
Barometric pressure is commonly measured in hectopascals (hPa) for international weather reports, inches of mercury (inHg) in the United States aviation and weather, millibars (mbar, equivalent to hPa), millimeters of mercury (mmHg), atmospheres (atm), bars, and pascals (Pa).
Is barometric pressure the same as atmospheric pressure?
Yes, barometric pressure and atmospheric pressure refer to the same physical quantity. Barometric pressure is simply the term used when the pressure is measured using a barometer, which is the standard instrument for weather stations worldwide.
What is normal barometric pressure in hPa and inHg?
Normal barometric pressure at sea level is 1013.25 hPa, which equals 29.92 inHg. In the US, weather reports typically use inHg, while most other countries use hPa. Pressures above 1030 hPa indicate high pressure (fair weather) and below 1000 hPa indicate low pressure (storms).
How does barometric pressure affect weather?
High barometric pressure (above 1013 hPa) typically brings clear skies and calm weather. Low barometric pressure (below 1013 hPa) is associated with clouds, wind, and precipitation. Rapidly falling pressure indicates an approaching storm, while rising pressure suggests improving weather.
Is this barometric pressure conversion tool free?
Yes, all calculators on Calculy are completely free to use. No registration or download is required. You can convert between all major barometric pressure units instantly in your browser.
What is the difference between hPa and mbar?
Hectopascals (hPa) and millibars (mbar) are numerically equivalent: 1 hPa = 1 mbar. The term millibar was traditionally used in meteorology, but the SI unit hectopascal is now the standard international unit for atmospheric pressure. Both are equal to 100 pascals.