The CI formula helps to find the interest earned on interest. In compound interest, interest may be compounded annually, half yearly, quarterly, annually with fractional years and annually with different rates at each year. You can find the formula for all type of compounding interest here.

a. Formula for Interest Compounded Annually

Total Amount = P(1+(R/100))

b. Formula for Interest Compounded Half Yearly

Total Amount = P(1+(R/200))

c. Formulae for Interest Compounded Quarterly

Total Amount = P(1 + (R/400))

d. Formulae for Interest Compounded Annually with fractional years (e.g 2.5 years)

Total Amount = P(1 + (R/100))

here if year is 2.5 then a =2 and b=0.5

e. With different interest rates for different years

Say x% for year 1, y% for year 2, z% for year 3

Total Amount = P(1+ (x/100)) x (1+(y/100)) x (1+(z/100))

Where,

CI = Compound Interest,

P = Principal or Sum of amount,

R = % Rate per annum,

n = Time Span in years

CI is beneficial for any type of savings but it is suggestable for any type of borrowing.