Investing
Compound Interest Calculator
Watch the eighth wonder of the world at work. See how steady contributions plus compounding turn modest savings into real wealth — and exactly how much is "free" interest.
Future value
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Interest earned
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Money sitting in checking earns nothing.Even a high-yield savings account or low-cost index fund puts compounding to work.
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Your money over time
Total balanceYour contributions
The widening gap between the two lines is compound interest — the longer you stay invested, the faster it grows.
Why starting early beats investing more
Compounding rewards time more than amount. Someone who invests $300/month from age 25 to 35 and then stops often ends up with more than someone who invests $300/month from 35 to 65 — because the early money had decades to compound. Move the "Years" slider above to feel it.
Rule of 72: divide 72 by your return to estimate how long money takes to double. At 7%, that's about every 10 years.