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Aviation Pressure Unit Converter

Convert between Pascal, hPa, Bar, PSI, mmHg, inHg, and standard atmosphere (atm) for aircraft systems, cabin pressurization, and altimeter calibration. Used by AMEs, pilots, and engineers for maintenance, flight planning, and troubleshooting.


Pressure Conversion Tool


Why Pressure Unit Conversion Matters in Aviation

Accurate pressure conversions are critical for:

Standard Aviation Pressure Reference

Condition hPa inHg psi
Standard Sea Level 1013.25 29.92 14.7
Tropopause (36,000 ft) 226.32 6.68 3.27
Cabin Differential (typical) — — 8.0

Source: ICAO Standard Atmosphere, FAA AIM §7-2-2

Pressure Conversion FAQ

It is largely regional. The United States, Canada, and parts of Japan use inches of Mercury (inHg), rooted in the Mercury barometer. Most of the rest of the world and ICAO standards use Hectopascals (hPa), which is equivalent to millibars (mb).

PSI (Pounds per Square Inch) is the standard for Boeing and most US-manufactured aircraft hydraulics (typically 3,000 psi). Bar is frequently seen on Airbus systems and European ground support equipment.

Pro tip: 1 Bar is approximately 14.5 PSI.

This is a unit converter, meaning it converts the mathematical magnitude between units. However, in aviation:
  • Absolute Pressure (PSIA): Pressure relative to a vacuum (used in altimeters).
  • Gauge Pressure (PSIG): Pressure relative to ambient atmospheric pressure (used in tire or oxygen bottle pressure).
Always ensure your maintenance manual specifies which one to use during testing.

$\Delta P$ is the difference between the internal cabin pressure and the external atmospheric pressure. Most commercial jets maintain a maximum differential of 8.0 to 9.0 PSI to ensure passenger comfort while minimizing stress on the aircraft fuselage.