How much will my money grow with compound interest?
Calculate how compound interest grows your investments over time. See the future value of your principal plus monthly contributions across any time horizon and compounding frequency.
What This Calculator Does
Compound interest is interest earned on both your original principal and on the interest that has already accumulated. It's the mechanism behind long-term wealth building — your money earns money, and that money earns more money.
How It Works
The formula is A = P(1 + r/n)^(nt), where P is principal, r is the annual rate, n is compoundings per year, and t is time in years. This calculator also factors in regular monthly contributions, which compound from the date they're added. More frequent compounding produces a slightly higher result.
Why It Matters
Compound interest is the single biggest factor in growing long-term wealth. The earlier you start, the more dramatic the effect — $200/month at 7% for 40 years grows to over $525,000, even though you only contributed $96,000.
Inputs
Results
Future Value
$144,572.72
What your investment will be worth
This calculator provides estimates for informational purposes only.
Insights
What compounding does
Start sooner if you can
How Compound Interest Is Calculated
The formula is A = P(1 + r/n)^(nt), where P is principal, r is the annual rate, n is compoundings per year, and t is time in years. This calculator also factors in regular monthly contributions, which compound from the date they're added. More frequent compounding produces a slightly higher result.
fvPrincipal = principal*(1+r/n)^(n*years), r=annualRate/100, n=compounding periods/year per selected frequency (annually=1, semiannually=2, quarterly=4, monthly=12, daily=365). fvContributions computed via an effective monthly rate derived from the nominal compounding: effectiveMonthlyRate = (1+r/n)^(n/12) - 1, then standard ordinary-annuity FV formula over months=years*12. futureValue = fvPrincipal + fvContributions; totalContributions = principal + monthlyContribution*months; totalInterest = futureValue - totalContributions. Where: principal, monthlyContribution, annualRate (%), years, compoundingFrequency. Assumptions: lump-sum principal compounds at the chosen frequency while monthly contributions are converted to an equivalent effective monthly rate (not compounded at the chosen frequency directly); contributions at end of month; no fees/taxes.
Key Takeaways
- •Time matters more than amount — starting 10 years earlier often beats doubling your contribution
- •Reinvest dividends and interest to keep compounding working
- •7% is a reasonable long-term return for diversified U.S. equities (after inflation, closer to 5%)
- •Daily compounding only marginally beats monthly — don't pay extra for it
- •Tax-advantaged accounts (401k, IRA, HSA) shield compound growth from yearly taxes
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