No, you cannot calculate the GAI on the WISC-V yourself. If you need an official score report including the GAI, contact your examiner. If you're just curious, you may pm me.

The GAI is calculated using the sum of scaled scores of the two VCI, two FRI, and one of the VSI subtests. If the highest subtest scores are in those indices, then the GAI might be of interest. If they are not, then the GAI will probably be no higher than the FSIQ.

...pronounced like the long vowel and first letter of the alphabet...