Compound Interest Calculation Select what you want to calculate then enter the values in the respective rows and click find. Say if you want to calculate C.I. enter the values for P,R and n. I want to calculate Compound Interest (CI) Principal (P) Rate of Interest (R) Interest Compounded Annually Half-yearly Quarterly Principal or Sum [P] = Rate % per Annum [R] % Time Years [n] Compound Interest [C.I.]