How to calculate ESI amount from CTC (Gross = CTC - total liabilities)

can anyone please tell me how to calculate gross from CTC - because gross = CTC - total liabilities right in that liabilities esi contribution of employer also will come right, but for calculating esi = gross*4.75 %, so first we need to find the esic amount for calculating gross right. so can anyone help me out with this issue.

First to calculate Basic from CTC for example your CTC is 55900/-
calculate your Basic 30% to 50% from CTC ( 55900/- * 39.36% = 22002/- )
22002/- is your basic amount. now you calculate your HRA Basic * 50% (22002/-*50% = 11001/-) then Conveyance Allowance (1600/-), Medical Allowance (1250/-), Other / Special allowance/s ( 13530/-) etc,
Basic = 22002/-
HRA = 11001/-
Conveyance Allowance = 1600/-
Medical Allowance = 1250/-
Other Allowance = 13530/-
total Gross = 49383/-
employee contribution ESI Gross * 1.75%
Employer contribution ESI Gross * 4.75%
total = 6.50%
as per my knowledge please calculate your gross from CTC.