Banks calculate interest on daily balances in your savings bank account and credit the same to your account periodically. 

has not any formula for calculation................

Interest calculation rate is different as per respective bank. So we can not say its formula, as CA Suraj Lakhotia said bank interest calculated on daily balances in our saving bank account so it will obviously differ for bank and its account.
 

it means this will calculate on daily closing balance ????????????

ok