Compound Interest Calculator

What Will Your Money Grow To?

See the real power of compounding — what consistent investing actually builds.

40 years of growth
$
$
%

Or pick a real benchmark · approx. 10-yr avg return

Past performance does not predict future results.

Portfolio Over Time

253341495765
Growth

Portfolio at Age 65

$1.5M

$1,475,521

Total You Invest$250,000
Market Growth+$1,225,521
Your money (17%)Market growth (83%)

Growth Milestones

Age 30 (5yr)$49,973
Age 35 (10yr)$106,639
Age 40 (15yr)$186,971
Age 45 (20yr)$300,851
Age 50 (25yr)$462,290
Age 55 (30yr)$691,150
Age 60 (35yr)$1.0M
Age 65 (40yr)$1.5M

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The 7% Rule

The S&P 500 has averaged ~10% annually before inflation, ~7% after. Most financial planners use 7% for projections.

Start Earlier, Not Bigger

Starting 10 years earlier often beats doubling your contribution. Time is the most powerful variable.

Projections assume a fixed annual return. Actual market returns vary. Not financial advice — consult a fiduciary advisor.

Investment Calculator — Common Questions

How does compound interest work?

Compound interest means you earn returns on both your original investment and all the returns you've already accumulated. For example, $10,000 at 10% annual return earns $1,000 in year one. In year two, you earn 10% on $11,000 — that's $1,100. Over decades, this compounding effect becomes dramatic. $10,000 invested at 10% for 30 years grows to over $174,000 without adding another dollar.

What annual return should I use for the stock market?

The S&P 500 has historically returned about 10% annually before inflation, or roughly 7% after inflation (real return). For a conservative long-term projection, most financial planners use 6–7% after inflation. For nominal (before-inflation) projections, 8–10% is commonly used. The actual future return is unknown — these are historical averages and past performance doesn't guarantee future results.

How much should I be saving for retirement?

The standard rule of thumb is to save 15% of your gross income for retirement, including any employer match. If you start later, you need to save more. A common target: have 1x your salary saved by 30, 3x by 40, 6x by 50, and 8x by 60. These are guidelines — your actual need depends on your expected expenses in retirement and when you plan to retire.

What is the 4% rule for retirement withdrawals?

The 4% rule states you can withdraw 4% of your portfolio in year one of retirement, then adjust for inflation each year, and have a high probability of your money lasting 30 years. On a $1 million portfolio, that's $40,000/year. This rule comes from historical research (the Trinity Study) and is widely used as a starting point, though some planners now suggest 3–3.5% for more conservative planning.

Is it better to invest a lump sum or contribute monthly?

Research consistently shows that lump sum investing outperforms dollar-cost averaging (monthly contributions) about two-thirds of the time, because markets tend to go up over time and a lump sum benefits from more time in the market. However, if you don't have a lump sum, monthly contributions through dollar-cost averaging is far better than not investing. Consistency matters more than timing.

What is the difference between a Roth IRA and a Traditional IRA?

A Traditional IRA gives you a tax deduction now and you pay taxes when you withdraw in retirement. A Roth IRA gives you no deduction now, but withdrawals in retirement are completely tax-free. If you expect to be in a higher tax bracket in retirement than now, Roth is usually better. For 2025, you can contribute up to $7,000 per year to an IRA ($8,000 if 50 or older).