$10,000 at 5% for 3 years
$10,000 × 0.05 × 3 = $1,500 interest. The final amount is $10,000 + $1,500 = $11,500.
Calculate simple interest, final amount, principal, annual rate, or time, with a year-by-year breakdown and an optional annual-compounding comparison.
Simple interest is calculated only on the original principal. The interest earned in one full year therefore stays constant when the principal and annual rate do not change.
This calculator converts months to years by dividing by 12 and days to years using 365 days per year. These conventions make the time value consistent across every solving mode.
Multiply principal by the annual rate as a decimal and time in years.
I = P × r × tAdd the simple interest to the original principal.
A = P + I = P(1 + rt)The rate and time must both be greater than zero.
P = I ÷ (r × t)Multiply the decimal result by 100 to display an annual percentage.
r = I ÷ (P × t)The result is in years and is also shown as approximate months and 365-day years.
t = I ÷ (P × r)$10,000 × 0.05 × 3 = $1,500 interest. The final amount is $10,000 + $1,500 = $11,500.
$200 interest on $1,000 over 2 years gives r = 200 ÷ (1,000 × 2) = 0.10, or 10% per year.
Simple interest uses the original principal throughout. Compound interest adds accumulated interest to the balance, so later interest can be earned on earlier interest.
Convert months or days consistently before using the annual-rate formula.
The comparison on this page assumes annual compounding and no recurring contributions.
Simple interest is interest calculated only on the original principal, rather than on the principal plus previously accumulated interest.
Multiply the principal by the annual interest rate as a decimal and the time in years: I = P × r × t.
The calculator divides the number of months by 12.
This calculator uses a stated 365-day year, so it divides days by 365.
Simple interest is based only on original principal. Compound interest can earn interest on accumulated interest as well.
Yes. Select the value you want to solve and enter the other required values. The calculator rejects combinations that would divide by zero.