Hi!
ESI is calculated on Basic + D.A. + All Allowances (e.g., HRA, Conv, O.T., etc.) + any other kind of earnings = Gross Amt. It is divided into two shares: 1.75% for the employee share and 4.75% for the employer share, totaling 6.5%.
All employees whose Gross Salary is 10,000 or less have to contribute towards ESI as 10,000 is the ceiling for ESI from 1st October 2006.
When you calculate it, if an amount comes in decimals, you have to round it off to the next rupee, e.g., if it is Rs 45.3, it will be taken as Rs 46.