What does this calculator find?
The hidden interest rate behind a deal. If you know how much you put in, how much it grows to, and over how long, it works backwards to the annual rate that connects them — assuming the interest compounds once a year.
// accounting › Loans & Credit Analytics
Interest Rate Calculator
The implied annual interest rate that turns a principal into a known maturity amount.
r = (A / P)^(1/n) − 1
Frequently asked questions
How is the rate recovered from the formula?
Divide the final amount by the principal to get the total growth factor, take the n-th root to spread it evenly across the years, then subtract 1. Turn $1,000 into $1,500 over 5 years and the implied rate is (1500/1000)^(1/5) − 1, about 8.4% a year.
What is the effective annual rate?
The rate that captures the true yearly cost or return once compounding is taken into account. With simple annual compounding it matches the nominal rate; with more frequent compounding the effective rate would sit slightly higher.
How do I read the sensitivity chart?
The middle line grows at the implied rate. The lines above and below show what would happen at two percentage points higher or lower. The fan that opens up between them shows how even a small change in rate compounds into a large difference over time.
Where is this used in real life?
Comparing deposits — finding the true rate behind a 'double your money in 9 years' claim (about 8%). Loans — uncovering the effective rate when only the total repayment is quoted. Investments — back-solving the annual return that took a starting balance to today's value, so you can compare it fairly against other options.