See exactly how your money grows over time. The most powerful force in investing — visualized instantly.
📊 Calculate Your Investment Growth
How much you're investing today
Regular monthly additions
S&P 500 historical average (inflation-adjusted): ~7% · Nominal: ~10.5%
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Total portfolio value
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Total Invested
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Interest Earned
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Money Multiplied
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Monthly at 4% SWR
Growth Over Time
How Compound Interest Works
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Einstein reportedly called it "the eighth wonder of the world" — whether he said it or not, the math is remarkable.
The formula: A = P(1 + r/n)^(nt) + PMT × [((1 + r/n)^(nt) - 1) / (r/n)]
Where P = principal, r = annual rate, n = compounds per year, t = years, PMT = monthly payment.
What annual return should I use?
The S&P 500 has returned approximately 10.5% nominally and 7% inflation-adjusted over long periods. For conservative planning, use 6–7%. For aggressive scenarios, 10%. Never count on returns above 12% for long-term planning.
How often should I compound?
Most investments compound monthly or daily. The difference between monthly and daily compounding is minimal — a $10,000 investment at 7% for 20 years grows to $40,388 (monthly) vs $40,495 (daily). Monthly is the standard assumption.
What is the Rule of 72?
Divide 72 by your annual return rate to find how many years it takes to double your money. At 7%, money doubles every 72/7 ≈ 10.3 years. At 10%, it doubles every 7.2 years.
Next Step
🏦 Maximize Returns With the Right Account
Compound interest in a Roth IRA is completely tax-free. See which retirement account is right for your tax situation.
