Interest Rate Finder
Find the implied interest rate when you know the present value, future value, and number of periods.
Reverse-engineer any growth rate.
Implied Interest Rate
Finding the interest rate from present value, future value, and periods:
r = (FV / PV)^(1/n) − 1
Where:
- r = interest rate per period
- FV = future value
- PV = present value
- n = number of periods
This is also known as CAGR (Compound Annual Growth Rate) when periods are years.
Examples:
- Investment grows from $10,000 to $15,000 in 5 years → 8.45% annual rate
- Home value goes from $200,000 to $350,000 in 10 years → 5.76% CAGR
- Stock from $50 to $200 in 20 years → 7.18% CAGR
Real vs nominal rate:
- Nominal rate = stated rate
- Real rate ≈ nominal rate − inflation rate
- If investments grew 8%/year but inflation was 3%, real return ≈ 5%
Rule of 72: To estimate how long it takes to double your money:
Years to double ≈ 72 / interest rate