How is the hydraulic grade calculated

I would like to know the equation the model uses to calculate the Hydraulic grade. Because I want to calculate the hydraulic grade line for my field results in order to compare it with the model results but I cannot figure out how the model is calculating the HGL. Because from what I found 1 bar is equivalent to 10.199773339984 m of head. So I would then simply multiply the measured  pressures in bar by that number and then ad the result to the elevation. So to test that I took the pressures predicted by the model and calculated the HGL using that method but I get different results then the HGL that the model produces (see the results in the table below). And also the way I calculate the Hydraulic grade I get a hydraulic grade that is higher than the hydraulic grade of my boundary element (a reservoir) which does not make sense since there are no pumps or prv’s downstream of the reservoir.

Hydraulic grade of the boundary element

Pressure from model prediction (bar)

Node Elevations (m)

Hydraulic grade from model prediction

Hydraulic grade calculated by me

44.91

 

3.6

7.87

44.81

44.59

3.6

8.21

44.81

44.93

4.2

2.14

44.81

44.98

4.3

0.98

44.81

44.84

3.9

5.3

44.81

45.08

3.4

9.98

44.81

44.66