How to calculate total GMAT score? The maximum possible score is 800.

Divided by sections:


AWA: maximum is 6 (from 0 to 6);
Integrated reasoning: maximum is 8 (from 1 to 8);
Math: maximum is 60;
Verbal: maximum is 60.


If to summarize these maximum results in each section then we will have 134, but not 800.
What is the right way to calculate total GMAT score?
The total score (which ranges from 200 to 800 in 10-point increments) is a scaled combination of the quantitative and verbal scores. 

There is no official "right way" to calculate the total score because the official conversion scale has not been made public. You can find various unofficial (estimated) conversion scales around the Internet - e.g. here, here, and here.