O-Level & A-level grades to gpa

Can someone give a rough estimate of my gpa
O-levels: 2A*, 5A, 1B
A-levels: 2A, 1B

just want to know where i stand in comparison

British Grade -> points
A*, A -> 4
B-> 3.7
C-> 3
D-> 2.7
E-> 2
F-> 1.7
G->1
U/0->0

Add your O’Level numbers, divide by 8 =x

Then, add points for A levels, divide by 3 =y

(x+y) /2 =GPA