How do you calculate the required interest rate?

The required rate r = (FV/PV)^(1/n) - 1, where FV is future value, PV is present value, and n is the number of years. This gives the annual compound rate needed.

What is the Rule of 72?

The Rule of 72 estimates how long it takes to double money: divide 72 by the annual interest rate. For example, at 6% per year, money doubles in roughly 12 years.

How is monthly rate related to annual rate?

The monthly equivalent rate is (1 + annual rate)^(1/12) - 1. This accounts for compounding and is slightly less than simply dividing the annual rate by 12.

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Interest Rate Calculator

Find the required interest rate given present value, future value, and time.

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Future Value ($)

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How to Solve for Interest Rate

This calculator solves for the interest rate using the compound growth formula: r = (FV/PV)^(1/n) - 1. It answers questions like "What annual return do I need to double my money in 10 years?" or "What rate did my investment actually earn?" For projecting what a known rate will produce, use our Compound Interest Calculator.

The monthly equivalent rate is useful for comparing investments that compound at different frequencies. Once you know your required rate, you can use our Investment Calculator to see the impact of regular contributions on top of that growth rate.

This is also useful for evaluating historical returns: enter what you invested and what it's worth today to find your annualized rate of return.

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For a related calculation, use Auto Loan Calculator to calculate car loan payments including trade-in value, down payment, and sales tax. Alternatively, use APR Calculator to calculate the true Annual Percentage Rate of a loan including fees and points.