Compound Interest Calculator

Compound interest calculator visualizes investment growth with monthly contributions. See how your money compounds over time with interactive charts. Calculate retirement savings and investment returns.

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$0$1,000,000
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$0$10,000
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yr
1 yr50 yr

Investment Growth

Future Value$300,851
Total Contributions$130,000
Total Interest Earned$170,851

Interest earned is 131% of your contributions

Your money earned $170,851 in interest over 20 years

Growth Over Time

What this means

  • • Consistency + time usually beat perfect timing.
  • • Fee control matters because costs compound too.
Test return scenarios

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Most visitors get better outcomes by comparing at least two scenarios.

Investment Return

Test return assumptions and contributions.

Retirement

Translate growth into retirement readiness.

Savings Goal

Plan cash goals alongside investing.

Compound Growth in Plain Terms

Returns generating additional returns is the core engine. In practice, time + consistency usually dominate outcomes.

Core Formula

A = P(1 + r/n)^(nt)

P = starting principal
r = annual return
n = compounding frequency
t = years invested

Levers That Matter Most

Start earlier

Extra years often beat larger late contributions.

Contribute consistently

Recurring deposits strengthen long-term growth.

Reinvest returns

Keeps the compounding engine running.

Control fees

Cost drag compounds too over decades.

Frequently Asked Questions

What is compound interest?
Compound interest means you earn returns on both your original money and past returns. Over time, that compounding can accelerate growth.
How often should interest be compounded?
More frequent compounding helps, but the biggest drivers are contribution amount, return rate, and time horizon.
What is the Rule of 72?
Rule of 72: divide 72 by annual return to estimate doubling time. At 8%, money roughly doubles in about 9 years.
How does compound interest differ from simple interest?
Simple interest is earned only on principal. Compound interest is earned on principal plus prior gains, so long-term totals are usually much higher.
What is a realistic rate of return to expect?
For planning, many people use conservative long-term assumptions (for example, lower than headline stock returns). Choose a rate that matches your risk level and asset mix.

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