Simple interest calculator help


Settings Remark
Interest rate (R) The interest rate (R) is expressed as percentage (%) per interest period.

The interest rate may contain max two digits after its decimal point.
The interest rate entered may contain a comma (,) or point (.) as a decimal point separator.

Correct entered interest rates
5.25
5,25
4

Incorrect entered interest rates
5.041

You can choose between the following interest periods:
  • day
    For example: 4.5% per day

    Every day the interest will be calculated on the principal amount for the specified time period (T).

  • week
    For example: 4.5% per week

    Every week the interest will be calculated on the principal amount for the specified time period (T).

  • two weeks
    For example: 4.5% per two weeks

    Every two weeks the interest will be calculated on the principal amount for the specified time period (T).

  • half month
    For example: 4.5% per half month

    Every half month the interest will be calculated on the principal amount for the specified time period (T).

  • month
    For example: 4.5% per month

    Every month the interest will be calculated on the principal amount for the specified time period (T).

  • two months
    For example: 4.5% per two months

    Every two months the interest will be calculated on the principal amount for the specified time period (T).

  • quarter
    For example: 4.5% per quarter

    Every quarter the interest will be calculated on the principal amount for the specified time period (T).

  • half year
    For example: 4.5% per half year

    Every half year the interest will be calculated on the principal amount for the specified time period (T).

  • year
    For example: 4.5% per year

    Every year the interest will be calculated on the principal amount for the specified time period (T).
The interest rate (R) and time period (T) should be in the same time units such as weeks, months, years etc. If they differ the calculator will adjust the time period accordingly.

Example 1: How time period will be adjusted:
Interest rate = 5% per month
Time period = 7 weeks

52 weeks equals 12 months equals 1 year
Thus 7 weeks equals (7*12)/52 = 1.615384 months

Example 2: How time period will be adjusted:
Interest rate = 5% per two weeks
Time period = 2 quarters

4 quarters equals 26 two weeks equals 1 year
Thus 2 quarters equals (2*26)/4 = 13 two weeks

Example 3: How time period will be adjusted:
Interest rate = 5% per half year
Time period = 2 half months

24 half months equals 2 half years equals 1 year
Thus 2 half months equals (2*2)/24 = 0.166667 half year

The simple interest equation:
FV = P + I
I = P * R * T
FV = P + P * R * T
P * R * T = FV - P
R = (FV - P) / (P * T)

where:
FV = Future value
I = Interest amount
P = Principal amount
R = Interest rate (as a decimal, not in percentage)
T = Time period