Simple interest is a calculation of interest that doesn’t take into account the effect of compounding. In many cases, interest compounds with each designated period of a loan, but in the case of simple interest, it does not. The calculation of simple interest is equal to the principal amount multiplied by the interest rate, multiplied by the number of periods.
For a borrower, simple interest is advantageous, since the total interest expense will be less without the effect of compounding. For a lender, compound interest is advantageous, as the total interest expense over the life of the loan will be greater.
Simple Interest Equation
A = P(1 + rt)
Where:
A = Total Accrued Amount (principal + interest)
P = Principal Amount
I = Interest Amount
r = Rate of Interest per year in decimal; r = R/100
R = Rate of Interest per year as a percent; R = r * 100
t = Time Period involved in months or years
From the base formula, A = P(1 + rt) derived from A = P + I and since I = Prt then A = P + I becomes A = P + Prt which can be rewritten as A = P(1 + rt)
Simple Interest Formulas and Calculations:
Use this simple interest calculator to find 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=R/100; 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), solve for A
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)