Interest Rate Calculator
Estimate the annual interest rate implied by a starting amount, ending amount, and time period.
Interest Rate Calculator tool
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Simple interest uses A = P(1 + rt). Compound interest uses A = P(1 + r/n)^(nt).
Privacy: calculations run locally in your browser. No inputs are stored or transmitted.
In simple interest mode, the annual rate is solved from: r = (A / P − 1) / t
In compound mode, the annual nominal rate is solved from: r = n[(A / P)^(1/(nt)) − 1] where n is the number of compounding periods per year.
Examples
- $1,000 growing to $1,200 over 2 years → solve the implied annual rate
- Switch to compound mode to estimate a rate under monthly compounding
- Use larger compounding frequency if you want a more frequent growth model
FAQ
- What does this interest rate calculator solve?
It estimates the annual interest rate from a starting amount, ending amount, and time period.
- What is the difference between simple and compound interest?
Simple interest grows only on the principal, while compound interest grows on both principal and accumulated interest.
- Can I choose compounding frequency?
Yes. In compound mode you can choose yearly, monthly, or daily compounding.
- Does this calculator guarantee investment returns?
No. It only solves a mathematical rate from the values you enter.
- Are my inputs stored?
No. All calculations run locally in your browser and are not stored or transmitted.