Compound Interest Calculator

The most powerful force in finance. See what time + consistency builds.

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📉 Waiting is compound interest, pointed at you

The same arithmetic that makes a head start powerful makes a delay expensive. Saving $500/month at 7% for 30 years builds about $603,000; starting five years late and stopping 30 years after your first payment leaves roughly $205,000 less — and catching up takes $753/month, not $500. See the math, with the sources — updated monthly from Freddie Mac, Case-Shiller and Census data.

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How This Works

Compound interest is interest earned on interest. As your investment grows, each period's return is calculated on a larger base, creating exponential growth over time.

The Rule of 72: Divide 72 by your annual return rate to estimate how many years it takes to double your money. At 8% return, your money doubles roughly every 9 years.