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Finance

Compound Interest & Savings Calculator

How does your money grow? Calculate the future value of a starting amount plus monthly contributions — final balance, total contributions and interest earned, in dollars.

Examples Index investing, 30 yrsHigh-yield savings 4.5%, 5 yrsJust $500/mo, 20 yrs

Endkapital

$219,268.52

nach 25 Jahren

Eingezahlt
$70,000.00
Zinsertrag
$149,268.52

Key facts

  • Rule of 72: at a 7% annual return your money roughly doubles every ~10 years (72 ÷ 7 ≈ 10.3).
  • Example: $10,000 plus $200/month for 30 years at 7% grows to about $325,000 — only $82,000 of that is contributions, about $243,000 is interest.
  • Time beats contribution size: most of the interest accrues in the final years — starting earlier matters more than paying in more.

FAQ

What is compound interest?
Interest is added to your balance and itself earns interest in the following period. Over long horizons the balance grows exponentially rather than linearly — interest makes up an ever larger share over time.
Can I use it for a savings account?
Yes. Set the monthly contribution to 0 and the calculator only compounds the starting amount — like a high-yield savings account or CD. Add a monthly amount to model regular investing.
Are taxes and inflation included?
No, deliberately not. It shows the gross balance before federal/state taxes and inflation so the pure compounding effect stays visible. Taxes on interest, dividends and capital gains, plus inflation, will reduce the real, after-tax result.

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