Compound Interest Calculator

Watch your money grow over time with compound interest

What is this? Compound interest is interest on interest — the most powerful force in personal finance. Einstein allegedly called it the 8th wonder of the world. This calculator shows exactly how your money grows with regular contributions, and how inflation erodes real purchasing power.

The rule of 72: Divide 72 by your interest rate to estimate how many years to double your money. At 7% return, money doubles every ~10.3 years.

Who it's for: Anyone saving for retirement, a house, education, or any long-term financial goal.
Starting & Contributions
Growth Results
Total Contributed
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Interest Earned
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Final Balance
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Real Value (Inflation-Adj.)
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Doubling Time
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Effective Annual Rate
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Year-by-Year Growth

Past performance does not guarantee future results. Actual investment returns vary. Not financial advice.

Grow Your Money Faster

Compound interest works best when you automate contributions. These tools make it effortless.

Gusto — Payroll & HR →
$300 per paid new customer through PartnerStack — payroll, benefits, onboarding
Betterment →
$1,250 per referred client who funds $50K+ — automated investing, retirement
Wealthfront →
$100 per referred client through Impact.com — low-cost index investing, 529 plans
ToolBest ForAffiliate Rate
Betterment ⭐⭐⭐Automated investing, retirement$1,250/ref (Impact)
Gusto ⭐⭐Payroll & HR for small biz$300/ref (PartnerStack)
Wealthfront ⭐Low-cost index investing$100/ref (Impact)
M1 FinanceHybrid brokerage + bankingNo affiliate

We may earn a commission if you click above. Calculator is free to use.

Frequently Asked Questions

What is compound interest?

Interest earned on both your principal AND the interest that has already been credited to your account. Compounding accelerates growth exponentially over time — the earlier you start, the more dramatic the effect.

What's the difference between APR and APY?

APR (Annual Percentage Rate) is the stated interest rate. APY (Annual Percentage Yield) includes the effect of compounding. For investment accounts, APY is what matters. For loans, APR is the true cost.

How often should I compound?

More frequent compounding is better. Daily > monthly > quarterly > annually. In practice, most savings accounts compound daily or monthly. Check what frequency your account uses.

What is the Rule of 72?

Divide 72 by your annual return rate to estimate how many years to double your money. At 8% return, 72 ÷ 8 = 9 years to double. This is an approximation, not exact science.

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