Let x be your score out of 50 points.
Compute the number (x-19)/7. (Where this formula comes from.)
The result is a number that represents the grade in terms of the standard
"g.p.a." interpretation:
Important:
It is the *numerical* score that is carried forward for later use in
final grade calculation.
That is, the difference between 2.4999 and 2.5001 is no greater than
the difference between 2.5001 and 2.5003.
Numerical values less than -1 are rounded up to -1 and those above
5 are rounded down to 5.
Here is a picture of the class results. The columns represent
the number of students getting a particular score, using the scale on the
left.