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Compound Interest Calculator

Calculate how your investments grow over time with compound interest.

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What is Compound Interest?

Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest, which only earns interest on the original amount, compound interest allows your money to grow exponentially over time.

Albert Einstein reportedly called compound interest "the eighth wonder of the world," saying: "He who understands it, earns it; he who doesn't, pays it."

The Compound Interest Formula

The basic formula for compound interest is:

Where:

For continuous compounding, the formula becomes:

The Rule of 72

A quick mental math trick to estimate how long it takes to double your money:

For example:

The Rule of 72 is a quick approximation. For more precise calculations, use the formula above or our calculator!

Why Compound Frequency Matters

The more frequently interest compounds, the more you earn. Think of it as: how often the bank calculates and adds interest to your balance.

At a 10% annual rate on $10,000 over 10 years:

Tips for Maximizing Compound Interest

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