How to calculate CUSTOM duty charges?

Assume - Ex Rate = 50 INR in 1 usd

Total inv value is 30000 usd

Freight charges is Rs 1000 usd

Insurance-1.125 % on inv value.

So formula is- total usd= (inv value + freight + insurance)

Now,

Total Inr= total Usd * ex rate

Lading charges = 1% of total inr

rest add the excise as applicable.