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Compound Interest Calculator

See how your money grows with daily, monthly or annual compounding. Includes regular contributions.

Final balance
$300,850.72
Final balance
$300,850.72
After 20 years
Total contributions
$130,000.00
Interest earned
$170,850.72
Effective annual rate
7.23%

Growth over time

  • 100% private

    All math runs in your browser. Nothing leaves your device.

  • Formula-verified

    Each calculator is unit-tested against authoritative sources.

  • Instant results

    Static-rendered pages. Sub-second loads on any device.

  • Works offline

    Visit once and it keeps working without an internet connection.

How to use the Compound Interest Calculator

  1. 1

    Enter your inputs

    Fill in the required fields at the top of the compound interest calculator. Each input shows a default placeholder so you can see the expected format and units before you type.

  2. 2

    Adjust assumptions and options

    Use the toggles, sliders and dropdowns to tailor the calculation to your situation — currency, country, time period, advanced options and any optional fields all change the result in real time.

  3. 3

    Review the result

    The result card updates instantly as you type. Read the headline number, then check the breakdown, chart and any per-period schedule to understand how the inputs combined to produce the answer.

  4. 4

    Compare scenarios

    Change one input at a time to see how sensitive the result is to that variable. This is how you build intuition: small changes that move the answer a lot are the levers that matter.

  5. 5

    Share or save your result

    Copy the shareable link to send the exact scenario to someone else, or use your browser to print or save the page. The URL preserves every input so the recipient sees the same answer you do.

Frequently Asked Questions

  • Compound interest is interest earned on both your original principal and accumulated interest. Unlike simple interest, your money grows exponentially over time — Einstein reportedly called it "the eighth wonder of the world".

  • More frequent compounding (daily vs annual) results in slightly higher returns because interest is added back more often. The difference is meaningful over long periods or with large balances.

  • EAR is the actual annual return after accounting for compounding. For a 6% nominal rate compounded monthly, EAR = (1 + 0.06/12)^12 ? 1 = 6.17%.

  • Yes — for retirement and savings planning, regular contributions dramatically increase final balances. The calculator supports monthly, quarterly or annual contributions.

  • Yes — broad market index funds historically average 7%–10% annual returns over multi-decade periods, though year-to-year volatility is significant. Use a conservative 6%–7% for long-term planning.

  • Divide 72 by your annual return rate to estimate years to double your money. At 8%, money doubles every ~9 years. It's a quick mental shortcut, accurate within ~1% for rates between 6% and 10%.

  • No — the calculator shows nominal returns. To estimate real (inflation-adjusted) returns, subtract expected inflation (~2-3%) from your assumed return rate.

  • No — for tax-advantaged accounts (Roth IRA, ISA, etc.) the nominal figure is your real return. For taxable accounts, subtract your marginal rate from gains.

  • Yes — set monthly contribution to zero. The calculator becomes a pure compound growth model.

  • Time is the most powerful variable in compounding. $5,000 invested at age 25 at 7% becomes ~$74,000 at 65. The same $5,000 invested at age 45 becomes only ~$19,000.

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