Investment Calculator
Compound growth with contributions
Enter your investment details to see projected growth and returns.
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How Investment Returns Work
$500 a month invested at 7% for 30 years grows to about $610,000: $180,000 of your own money and about $430,000 of growth, with monthly compounding. A one-time $10,000 at the same rate becomes $81,165. Enter your starting amount, contributions, return and time above to see your final value, total return and a year-by-year chart.
Compound interest is the process where earnings generate their own earnings over time. The longer your money is invested, the more powerful this effect becomes. At 7% annual return, $10,000 doubles in approximately 10 years without any additional contributions: and every contribution you add compounds separately from that point.
Regular contributions are often more important than the initial investment. Investing $500/month for 20 years at 7% gives about $260,000: $120,000 of your own money and about $140,000 of growth. At 30 years growth pulls far ahead: $180,000 contributed and about $430,000 of growth.
The Rule of 72
Divide 72 by your annual return rate to estimate how long your money takes to double. At 7%: 72/7 = 10.3 years. At 8%: 9 years. At 10%: 7.2 years. At 4%: 18 years. This works because 7% compounded annually is approximately 2x every decade.
Expected Returns by Asset Class
Historical averages (before inflation): S&P 500 index: ~10% nominal, ~7% real. Bonds (10yr Treasury): ~4-5%. Real estate: ~4-6% capital appreciation + rental yield. Gold: ~2-3% real long-term. Diversified global portfolio: typically 6-9% nominal depending on allocation.
Impact of Fees
A 1% annual fee on a 7% return effectively reduces your return to 6%, which removes about 28% of the gains over 30 years. Over 30 years on $10,000 initial: 7% = $76,123. 6% = $57,435. The $18,688 difference is entirely from fees. Index funds with 0.03-0.10% expense ratios dramatically outperform actively managed funds over long periods.
Inflation Adjustment
With 3% average inflation, a 7% nominal return is approximately 4% in real (purchasing power) terms. $100,000 that grows to $200,000 in 10 years at 7% only has purchasing power equivalent to ~$149,000 in today's dollars. Always consider real returns when planning long-term financial goals.
Investment Growth Reference Tables
$10,000 invested once, compounded monthly
| Annual return | 10 years | 20 years | 30 years |
|---|---|---|---|
| 4% | $14,908 | $22,226 | $33,135 |
| 6% | $18,194 | $33,102 | $60,226 |
| 7% | $20,097 | $40,387 | $81,165 |
| 8% | $22,196 | $49,268 | $109,357 |
| 10% | $27,070 | $73,281 | $198,374 |
$500 invested at the end of every month
| Annual return | 10 years | 20 years | 30 years |
|---|---|---|---|
| You invest | $60,000 | $120,000 | $180,000 |
| 4% | $73,625 | $183,387 | $347,025 |
| 6% | $81,940 | $231,020 | $502,258 |
| 7% | $86,542 | $260,463 | $609,985 |
| 8% | $91,473 | $294,510 | $745,180 |
| 10% | $102,422 | $379,684 | $1,130,244 |
With the calculator's default inputs ($10,000 plus $500 a month at 7% for 20 years) you invest $130,000 and end with about $300,850.
How Fees Shrink the Result
$10,000 up front plus $500 a month for 30 years, with a 7% return before fees. The fee is taken as a lower yearly return.
| Yearly fee | Value after 30 years | Cost of the fee |
|---|---|---|
| None | $691,150 | $0 |
| 0.03% (large index ETF) | $686,829 | $4,321 |
| 0.5% | $623,007 | $68,143 |
| 1.0% | $562,483 | $128,667 |
| 1.5% | $508,680 | $182,470 |
A 1% advisory or fund fee looks small, but here it costs more than half of everything you contributed ($190,000). Check the expense ratio of every fund you hold.
Taxes, Inflation and Account Choice
2026 capital gains tax
Gains on investments held more than a year are taxed at 0% while taxable income is up to $49,450 (single) or $98,900 (married filing jointly), 15% up to $545,500 or $613,700, and 20% above that. The 3.8% net investment income tax adds to it once modified AGI passes $200,000 (single) or $250,000 (joint). Gains on assets held a year or less are taxed like wages. See the capital gains tax calculator for your own numbers.
Inflation
The calculator shows nominal dollars. $100,000 received 20 years from now buys what about $67,297 buys today at 2% inflation, $55,368 at 3% and $45,639 at 4%. For a result in today's dollars, enter your return minus inflation as the rate.
Tax-advantaged accounts first
For 2026 you can put $24,500 in a 401(k) and $7,500 in an IRA ($8,600 at 50 and over). Growth inside these accounts is not taxed each year, so the same return compounds faster than in a taxable account.
Method and sources. Lump sums: P(1 + r/12)12t. Monthly investments: end-of-month annuity D × ((1 + r/12)12t − 1) ÷ (r/12). Fees are modeled as a lower annual return. Inflation: value ÷ (1 + inflation)years. All figures computed with these formulas. Tax figures: IRS Rev. Proc. 2025-32 (2026 capital gains brackets) and IRS guidance on the net investment income tax. Contribution limits: IRS Notice 2025-67. Returns are not guaranteed; projections only.
This calculator provides projections for illustrative purposes only. Investment returns are not guaranteed and actual results will vary. Past performance does not predict future results. All investing involves risk, including possible loss of principal.
Frequently Asked Questions
Compound interest means you earn returns on your returns, not just on the original principal. Year 1: $10,000 at 7% earns $700, balance $10,700. Year 2: 7% of $10,700 earns $749, balance $11,449. The extra $49 in year 2 vs year 1 is compound interest at work. Over 30 years, this snowball effect is enormous: $10,000 grows to $76,123 without any additional contributions. Adding regular contributions accelerates this dramatically.
Historical annual returns (nominal, before inflation): S&P 500 index: ~10% per year (1926-present). S&P 500 real return (after inflation): ~7%. Balanced portfolio (60% stocks, 40% bonds): ~6-8%. Conservative portfolio: ~4-5%. Individual stocks: highly variable. For long-term planning, financial advisors typically model 5-7% real returns for stock-heavy portfolios. Using 7% nominal is common for retirement projections and aligns with recent index fund performance.
The standard recommendation is 15-20% of gross income for retirement, including any employer match. For general wealth building: invest whatever remains after covering essential expenses and maintaining an emergency fund. Even small amounts matter significantly due to compounding: $100/month for 30 years at 7% grows to $121,997. $200/month grows to $243,994: exactly double. The amount matters, but starting early matters more.
Dollar-cost averaging (DCA) is investing a fixed amount at regular intervals regardless of market conditions. When prices are high, you buy fewer shares. When prices are low, you buy more. Over time, this averages out your purchase price and reduces the risk of investing a lump sum at market peaks. It is also psychologically easier: you automate contributions and remove the temptation to time the market. Research consistently shows most investors underperform the market by trying to time it. Regular automatic contributions are the practical implementation of DCA.
Nominal return is the raw percentage your investment grows. Real return adjusts for inflation. Formula: Real Return = (1 + Nominal) / (1 + Inflation) - 1. Approximate shortcut: Real Return = Nominal - Inflation. At 7% nominal with 3% inflation: real return is approximately 4%. This matters for long-term planning because $1,000,000 in 2050 will have significantly less purchasing power than today. For retirement planning, always check whether projections use nominal or real returns.
Research consistently shows lump sum investing outperforms dollar-cost averaging approximately 2/3 of the time when markets trend upward (which they do most of the time). A Vanguard study found lump sum investing beats DCA by an average of 2.3% over 12 months across US, UK, and Australian markets. However, the psychological comfort and risk reduction of DCA is real: if investing a lump sum would cause you to sell during downturns, DCA produces better real-world results. If you have a windfall and strong emotional discipline, lump sum is generally better mathematically.
Priority order for US investors: 1. 401(k) up to employer match (free money). 2. HSA if eligible (triple tax advantage: pre-tax in, grows tax-free, tax-free for medical). 3. Roth IRA up to annual limit ($7,500 in 2026, $8,600 if 50+). 4. 401(k) up to annual limit ($24,500 in 2026). 5. Taxable brokerage account. For non-US investors: use tax-advantaged accounts first (ISA in UK, TFSA/RRSP in Canada, etc.) before taxable accounts. The account type matters almost as much as the investment choices due to tax drag.
Short-term (under 3 years): stocks are too volatile. Use high-yield savings accounts, money market accounts, or short-term bonds. Medium-term (3-7 years): a mix of stocks and bonds is appropriate. Can handle some volatility with time to recover. Long-term (7+ years): higher stock allocation is appropriate, historically, the S&P 500 has never lost money over any 20-year period. The longer your horizon, the more risk you can take because you have time to recover from downturns. This is why target-date funds automatically shift from stocks to bonds as you approach retirement.
Sequence of returns risk is the danger that poor investment returns early in retirement (when you start withdrawing) can permanently damage a portfolio even if long-term average returns are good. Example: two retirees both average 7% over 20 years, but one has bad returns early and good returns late, while the other is reversed. The one with bad early returns runs out of money significantly sooner due to withdrawals locking in losses. This is why a cash/bond buffer (2-3 years of expenses) near and early in retirement is critical: it allows you to avoid selling stocks during downturns.
The most widely used rule is 25x your annual expenses (the inverse of the 4% withdrawal rule). If you spend $60,000/year, you need $1,500,000. At 4% withdrawal, this portfolio has historically lasted 30+ years with high probability. Factors that increase the needed amount: retiring early (longer time horizon), high spending, high taxes in retirement, uncertain health expenses. Factors that decrease it: Social Security/pension income, part-time work in early retirement, flexibility to reduce spending. Most planners recommend having 10x your final working salary saved by age 67.
At a 7% average return, compounded monthly, $10,000 grows to about $40,387 in 20 years. At 4% it becomes $22,226, and at 10% it becomes $73,281. Real stock returns vary a lot from year to year, so treat these as averages, not promises.
Long-term gains (assets held more than one year) and qualified dividends are taxed at 0%, 15% or 20%. The 0% rate applies while taxable income is up to $49,450 for single filers or $98,900 for joint filers, and 20% starts above $545,500 or $613,700. Short-term gains are taxed as ordinary income, and high earners may owe the extra 3.8% net investment income tax. Gains inside a 401(k) or IRA are not taxed until withdrawal, and never in a Roth if withdrawals are qualified.