Enter a present value, future value, and time period to calculate the implied simple and compound annual interest rate.
How to Use the Interest Rate Calculator
Present value, future value, and time period are the three inputs; the calculator solves backward for the rate rather than asking you to guess and check.
Sometimes the rate is the unknown — you know what you started with, what it became, and how long it took, and you want to work backward to the rate that explains it.
Simple Rate = (FV − PV) ÷ (PV × t)
Compound Rate = (FV ÷ PV)^(1/t) − 1Both answers come from the same three inputs; they diverge because they assume different growth mechanics. The simple-rate figure assumes flat, linear growth with no reinvestment of gains along the way. The compound-rate figure assumes the growth compounded smoothly every period — which is the more realistic assumption for most investments and loans, and the one usually meant by "annualized return" or "annual growth rate."