Is there any way (formula) to calculate the fuel consumption (e.g.
L/100 KM or Gal/Mil) from values read from OBD-II interface?

I think next values could be taken into consideration to compute the
fuel consumption, but I don't know how exactly to interpret the result
of them:

Short Term Fuel Trim
Long Term Fuel Trim
Mass Air Flow
Fuel Pressure
Accelerator Pedal Position
Throttle Position
RPM

Chris