Simple interest calculator help


Settings Remark
Days in year The number of days within a year can be set to:
  • 366 days
    This is a leap year (normal year + 1 day extra (29 feb)

  • 365 days
    Normal year (non leap year)
    Interest found using a 365-day year is called exact interest.

  • 364 days
    The 364 day year derives from 52 weeks * 7 day weeks = 364 days in a year.

  • 360 days
    When a month has 30 days, a year has 12 months * 30 = 360 days
    Interest found using a 360-day year is called ordinary interest.

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.

The number of days within a year is important when adjusting the time period especially when the day unit is used.

Example 1: How time period will be adjusted, a year has 366 days:
Interest rate = 5% per day
Time period = 2 months

366 days equals 12 months equals 1 year
Thus 2 months equals (2*366)/12 = 61 days

Example 2: How time period will be adjusted, a year has 365 days:
Interest rate = 5% per day
Time period = 2 months

365 days equals 12 months equals 1 year
Thus 2 months equals (2*365)/12 = 60.8333 days

Example 3: How time period will be adjusted, a year has 364 days:
Interest rate = 5% per day
Time period = 2 months

364 days equals 12 months equals 1 year
Thus 2 months equals (2*364)/12 = 60.6667 days

Example 4: How time period will be adjusted, a year has 360 days:
Interest rate = 5% per day
Time period = 2 months

364 days equals 12 months equals 1 year
Thus 2 months equals (2*360)/12 = 60 days