Question: how to calculate compound interest on rd?
Answer: Factors Affecting RD Interest Rates.
Banks or financial institutions use the following formula to calculate Interest on Recurring Deposit or maturity value of RD (suggested by Indian Bank Association)
M = R [(1+i)n – 1] divided by 1-(1+i)(-1/3)
M here stands for Maturity value of the RD. ... 
A = P (1 + r/n) ^ nt.