Dear Sir,
Let me elaborate on Mr. LN's answer with a small correction [typo].
Gratuity Calculation Formula
It's Last Drawn Basic + DA x 15 / 26 x number of years completed.
Assuming that your last drawn Basic + DA is Rs. 1,00,000 and you have worked for 6.2 years.
Your Gratuity Payment is = 1,00,000 x 15 / 26 x 6 = Rs. 3,46,153.8
* Note: If the years of service end in decimals, for the purpose of calculation, it will be rounded off to the nearest integer.