Barometric Pressure Weather & Aviation Converter

Aviation altimeters and US meteorology use Inches of Mercury (inHg) for QNH barometric pressure settings. International weather services and METAR reports use Hectopascals (hPa) or Millibars (mbar). Falling barometric pressure indicates approaching storm fronts.

To use the Barometric Pressure Weather & Aviation Converter, enter your Barometric Pressure Value, Unit to Convert From. The calculator instantly computes Inches of Mercury (inHg), Hectopascals / Millibars and more. Results update in real time as you change any input — no submit button needed.

How to Use This Calculator

Enter your Barometric Pressure Value (e.g. 29.92) and Unit to Convert From — choose from Inches of Mercury (inHg - US Altimeter), Hectopascals / Millibars (hPa / mbar), Millimeters of Mercury (mmHg). Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Standard Sea-Level Pressure = 29.92 inHg = 1013.25 hPa/mbar = 760.0 mmHg = 1.0000 atm

1 inHg = 33.8639 hPa/mbar = 25.40 mmHg

Worked Example

Convert US Altimeter setting 29.92 inHg:

29.92 inHg = 1013.25 hPa (mbar) = 760.0 mmHg = 1.0000 atm. Weather Status: Normal Sea-Level Standard.

Understanding Your Result

Unit conversions are exact by definition within a given measurement system (e.g., 1 km = exactly 1,000 m). Cross-system conversions (metric to imperial) use defined exchange factors: 1 inch = exactly 2.54 cm; 1 pound = 0.45359237 kg. Round your converted result to match the precision of your original measurement — expressing more decimal places than your input justifies implies false accuracy. For regulatory, legal, or safety-critical applications, verify which measurement system is required by the applicable standard.