How can I calculate QNH from QFE?
In metric:


1 milibar is approximately equal to 30 feet.  This calculation is therefore also approximate but is good for airfield elevations to several hundred feet since we round to the nearest millibar. 

Divide the airfield altitude in feet by 30 to get the number of millibars above MSL. Add this to the QFE to get QNH or subtract it from QNH to get QFE.

For example, the airfield elevation is 200 feet.  Dividing by 30 gives us 6.66r.  The QFE is 1023. Add 6.66 to get 1029.66 and round up to 1030 millibars, which is the QNH.


  In imperial:


1 inch mercury is approximately equal to 900 feet.  This calculation is therefore also approximate but is good for airfield elevations to several hundred feet since we round to the nearest hundredth inches. 

Divide the airfield altitude in feet by 900 to get the number of inches above MSL. Add this to the QFE to get QNH or subtract it from QNH to get QFE.

For example, the airfield elevation is 300 feet.  Diving by 900 gives us 0.33r.  The QFE is 30.12. Add 0.33 to get 30.45 which is the QNH.

If the airfield elevation is below sea level, subtract rather than add and vice versa.