Simple Interest Calculator (Principal + Interest)

Simple Interest Calculator Calculate: Total P+I (A) Principal (P) Rate (r) Time Period (t) Where: A = P(1 + rt) Principal (P): $     Rate (r):   % per day per month per quarter per year Time Period (t):     days months quarters years Answer: A = ? Equation: A = P(1 + rt) Calculation: ?

Simple Interest Equation (Principal + Interest)

Where:

• A = Total Accrued Amount (principal + interest)
• I = Interest Amount
• P = Principal Amount
• r = Rate of Interest per month or year (decimal)
• t = Time Period involved in months or years

From the base formula, A = P(1 + rt) derived from A = P + I and I = Prt so A = P + I = P + Prt = P(1 + rt)

Note that rate r and time t should be in the same time units such as months or years.  If you enter them differently this calculator will adjust the answer accordingly.  r is entered in % but converted and calculated in decimal form.

Time conversions are based on day count of 365 days/year, 30.4167 days/month and 91.2501 days/quarter.

Simple Interest Formulas and Calculations:

This calculator finds A, the Final Investment Value, using the simple interest formula: A = P(1 + rt) where P is the Principal amount of money to be invested at an Interest Rate r% per period for t Number of Time Periods.  Where r is in decimal form; r and t are in the same units of time.

The accrued amount of an investment is the original principal P plus the accumulated simple interest, I = Prt, therefore we have:

A = P + I = P + (Prt), and finally A = P(1 + rt)

• Calculate Total Amount Accrued (Principal + Interest)
  • A = P(1 + rt)
• Calculate Principal Amount, solve for P
  • P = A / (1 + rt)
• Calculate rate of interest in decimal, solve for r
  • r = (1/t)(A/P - 1)
• Calculate rate of interest in percent
  • R = r * 100
• Calculate time, solve for t
  • t = (1/r)(A/P - 1)

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