Learn how to change an altimeter from inHg to hPa, find the BARO unit selector, handle fixed gauges and avoid confusing hPa with STD.
In a general flight simulator, change the altimeter’s pressure unit at the aircraft’s BARO control: select HPA or MB instead of IN or IN HG, then enter the local QNH. Glass cockpits may place this option in a PFD menu; some analogue altimeters use fixed units and cannot be switched.
How do I switch the altimeter from inHg to hPa?
The change is usually made on the aircraft instrument rather than through the simulator’s general measurement settings.
- Identify the active altimeter. The main flight display, standby instrument and any co-pilot display may have independent barometric controls.
- Find the BARO unit control. Look around the BARO knob for labels such as
IN,IN HG,HPAorMB. In a glass cockpit, check its PFD or barometer menu. - Select HPA or MB. Hectopascals and millibars are numerically equivalent for altimeter settings, so
1016 hPais the same setting as1016 mb. - Enter the local QNH. Turn the BARO knob until the reported pressure appears. Our explanation of QNH, BARO controls and standard pressure covers where the value comes from and when it should be used.
- Check the result. On the ground with QNH selected, the indicated altitude should be close to the aerodrome’s published elevation.
A mistake we see constantly is pressing the BARO knob and selecting STD instead of changing units. STD sets standard pressure—normally displayed as 1013 hPa or 29.92 inHg—and is not an hPa/inHg selector.
Where is the hPa/inHg selector?
Its location depends mainly on the aircraft’s instrument type and the depth of its simulated avionics.
| Instrument type | Where to look | Common limitation |
|---|---|---|
| Glass-cockpit PFD | BARO menu, PFD settings or a softkey beside the pressure readout | The knob’s push action may select STD rather than units |
| Airliner flight display | On or beside the BARO selector on the flight-control or display panel | Captain and first-officer displays may be separate |
| Analogue altimeter | A physical unit selector, if the real instrument has one | Many gauges are fixed to inHg, hPa or a dual scale |
| Standby instrument | Its own knob or instrument menu | Changing the main PFD may not change the standby setting |
For Microsoft Flight Simulator 2024, the exact control still depends on the loaded aircraft. Our MSFS 2024 instructions for entering QNH and selecting STD explain the simulator-specific workflow without assuming every cockpit uses the same panel.
Why did changing the simulator’s units not change the cockpit?
Global metric or US-unit options often affect menus, weather reports or interface readouts without altering a modelled cockpit instrument.
The cockpit may reproduce a real altimeter whose face is permanently marked in one unit. Third-party aircraft can also implement their own avionics settings independently of the simulator. Likewise, a command that synchronises or adjusts barometric pressure may change the value while leaving its display unit untouched.
What if the aircraft cannot display hPa?
Use the instrument’s native unit and convert the reported pressure rather than forcing an unsupported display mode.
- hPa to inHg: divide by
33.8639. - inHg to hPa: multiply by
33.8639. - Standard pressure:
1013.25 hPaequals29.92 inHg.
Pressure groups reveal which unit a weather report uses: Q1016 means 1016 hPa, while A2992 means 29.92 inHg. See our guide to identifying pressure values in a METAR if the report is the source of the setting.
Should I use hPa or inHg?
Use the unit given by ATIS, ATC, the METAR or the procedure you are following; this avoids unnecessary conversion and entry errors.
InHg is commonly encountered in North American operations, while hPa is widely used elsewhere. If the cockpit offers both, choose the regional unit. If it does not, convert the number carefully—entering an hPa value while the display remains in inHg is the usual reason the knob appears to stop at an unexpected limit.