Interest Rate Calculator
Interest Rate Calculator
Sometimes you know the beginning and ending values of an investment or debt and the time elapsed, but not the rate itself — for example, an old investment statement, a family loan, or an investment that grew from 1,000 USD to 1,628.89 USD over 10 years. This calculator solves for the annually compounded rate that explains that growth.
Investors reviewing past performance use this to back out the effective annual return of an investment, and it's also useful for verifying whether an advertised or assumed rate on a loan or account actually matches its real growth history.
- Reverse-Engineers the Rate: Solves A = P(1+r)ⁿ for r, given P, A, and n (years).
- Assumes Annual Compounding: This calculates the equivalent annually-compounded rate; more frequent compounding at a lower stated rate could produce the same result.
- Useful for Verification: Check whether an investment's actual historical growth matches its advertised or expected rate.
What if I don't know the exact final amount?
Use your best estimate — the calculated rate will be an approximation proportional to the accuracy of your inputs. Small differences in the final amount can noticeably shift the computed rate over long periods.
Does this account for additional contributions during the period?
No — this assumes a single lump sum grew from the starting to the final amount with no additional deposits or withdrawals along the way.
Interest Rate Calculator
Sometimes you know the beginning and ending values of an investment or debt and the time elapsed, but not the rate itself — for example, an old investment statement, a family loan, or an investment that grew from 1,000 USD to 1,628.89 USD over 10 years. This calculator solves for the annually compounded rate that explains that growth.
Investors reviewing past performance use this to back out the effective annual return of an investment, and it's also useful for verifying whether an advertised or assumed rate on a loan or account actually matches its real growth history.
- Reverse-Engineers the Rate: Solves A = P(1+r)ⁿ for r, given P, A, and n (years).
- Assumes Annual Compounding: This calculates the equivalent annually-compounded rate; more frequent compounding at a lower stated rate could produce the same result.
- Useful for Verification: Check whether an investment's actual historical growth matches its advertised or expected rate.
What if I don't know the exact final amount?
Use your best estimate — the calculated rate will be an approximation proportional to the accuracy of your inputs. Small differences in the final amount can noticeably shift the computed rate over long periods.
Does this account for additional contributions during the period?
No — this assumes a single lump sum grew from the starting to the final amount with no additional deposits or withdrawals along the way.