Formula:

Total Amount = Principal + CI (Compound Interest)

a. Formula for Interest Compounded Annually
         Total Amount = P(1+(R/100))ⁿ

b. Formula for Interest Compounded Half Yearly
         Total Amount = P(1+(R/200))²ⁿ

c. Formulae for Interest Compounded Quarterly
         Total Amount = P(1+(R/400))⁴ⁿ

d. Formulae for Interest Compounded Annually with fractional years (e.g 2.5 years)
         Total Amount = P(1+(R/100))^a×(1+(bR/100))
         here if year is 2.5 then a =2 and b=5

e. With different interest rates for different years
Say x% for year 1, y% for year2, z% for year3
         Total Amount = P(1+(x/100))*(1+(y/100))*(1+(z/100))

where CI = Compound Interest, P = Principal or Sum of amount, R = % Rate per annum, n = Time Span in years

Online Compound Interest Calculation. Calculate Compound Interest, Principal, different Rate of Interest for Annual, Half yearly, Quartely and for Fractional years and daily, monthly interests is made much easier.