Investment Calculator

See how your money grows with compound interest, regular contributions, and year-by-year projections

Reference table

Initial Investment	Future Balance	Total Contributed	Interest Earned
100	$31,221	$24,100	$7,121
200	$31,386	$24,200	$7,186
250	$31,468	$24,250	$7,218
500	$31,880	$24,500	$7,380
750	$32,292	$24,750	$7,542
1,000	$32,703	$25,000	$7,703
1,250	$33,115	$25,250	$7,865
1,500	$33,527	$25,500	$8,027
2,000	$34,350	$26,000	$8,350
2,500	$35,174	$26,500	$8,674
3,000	$35,997	$27,000	$8,997
4,000	$37,644	$28,000	$9,644
5,000	$39,292	$29,000	$10,292
7,500	$43,409	$31,500	$11,909
10,000	$47,527	$34,000	$13,527

Investment Tips

Time beats timing: starting 10 years earlier matters more than doubling your contribution rate
A 1% fee doesn't sound like much, but over 30 years it can consume 25-30% of your returns
Dollar-cost averaging through regular contributions reduces the impact of market volatility
After maxing tax-advantaged accounts (401k, IRA), invest in low-cost index funds for taxable accounts

What Is an Investment Calculator?

An investment calculator projects how your money will grow over time using compound interest and regular contributions. Unlike a simple savings calculator, it accounts for real-world factors like inflation erosion, management fees, capital gains taxes, and increasing contributions over time. The power of compound interest means your money earns returns on both your original investment and your accumulated returns — creating exponential growth over long periods. Albert Einstein allegedly called compound interest the eighth wonder of the world, and whether or not the attribution is accurate, the math certainly is remarkable.

How Compound Interest Works

Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. With monthly compounding, your annual return is divided into 12 parts and applied each month, with each month's calculation including the interest earned in prior months. This creates a snowball effect: a $10,000 investment at 8% compounded monthly grows to $22,196 in 10 years, compared to $18,000 with simple interest — that's $4,196 more from compounding alone. The three key factors are: rate of return (higher = faster growth), time horizon (longer = dramatically more growth due to exponential curve), and contribution frequency (more frequent = more compounding periods).

Common Investment Types & Returns

S&P 500 Index Fund: Historical average ~10% annually (7% after inflation). Low fees (0.03-0.1%). Best for long-term passive investors.
Total Bond Market: Average 4-5% annually. Lower risk, lower return. Good for diversification and near-retirement portfolios.
Target-Date Funds: Automatically shift from stocks to bonds as you age. Typical fees 0.1-0.3%. Good for hands-off investors.
Individual Stocks: Can outperform or underperform dramatically. Most active traders underperform index funds over 10+ years.
REITs (Real Estate Investment Trusts): Average 8-12% historically. Provides real estate exposure without property ownership.
High-Yield Savings: Currently 4-5% APY. FDIC insured. No market risk but barely keeps pace with inflation.

The Hidden Cost of Fees

A 1% annual fee reduces a $500K portfolio by $170K+ over 30 years compared to 0.1% — that's like losing a third of your returns.
Index funds charge 0.03-0.20% annually. Actively managed funds charge 0.5-1.5%. Most actively managed funds underperform indexes.
Financial advisor fees (1% of assets) cost roughly $100K on a $500K portfolio over 20 years. Consider fee-only advisors.
Trading commissions are mostly free now, but bid-ask spreads and tax implications of frequent trading still cost money.
Fund expense ratios are deducted from returns automatically. A fund reporting 8% return with 1% fee actually earned 9%.
Compare total cost of ownership: management fee + expense ratio + transaction costs + tax efficiency.

Investment Growth Examples

See the dramatic effect of time, fees, and contributions on investment outcomes

$10K + $500/mo for 20 Years at 8%

Initial: $10,000
Monthly: $500 for 20 years
Total contributed: $10,000 + ($500 × 240) = $130,000
8% return, compounded monthly

Final balance: ~$316,000. You contributed $130K but earned $186K in interest — 59% of your wealth came from compound growth alone.

Impact of Starting 10 Years Earlier

Person A: $500/mo from age 25 to 65 (40 years)
Person B: $500/mo from age 35 to 65 (30 years)
Both at 8% annual return, monthly compounding

Person A: ~$1,745,000. Person B: ~$745,000. Starting 10 years earlier with the SAME contributions yields $1M MORE.

Frequently Asked Questions

What rate of return should I use?

For a diversified stock portfolio, use 7-10% (nominal) or 4-7% (inflation-adjusted). The S&P 500 has returned ~10% annually since 1926. For conservative estimates use 6-7%. For bonds or savings, use 3-5%. Always plan with conservative estimates to avoid disappointment.

How does compounding frequency affect returns?

More frequent compounding yields slightly higher returns. $10,000 at 8% for 10 years: annually = $21,589, monthly = $22,196, daily = $22,253. The difference between monthly and daily is minimal (~$57), so monthly compounding is a reasonable assumption for most investments.

Should I invest a lump sum or contribute regularly?

Historically, lump sum investing outperforms dollar-cost averaging about 2/3 of the time because markets tend to go up. However, dollar-cost averaging through regular contributions reduces risk and is more practical for most people who invest from paychecks.

How much do fees really matter?

Enormously over time. On a $500/month investment over 30 years at 8% return: with 0.1% fees you'd have $691K, with 1% fees you'd have $569K — a $122K difference, or 18% less wealth. Choose low-cost index funds with expense ratios under 0.2%.

What is the Rule of 72?

Divide 72 by your annual return to estimate how many years it takes to double your money. At 8% return: 72 ÷ 8 = 9 years to double. At 10%: 7.2 years. At 6%: 12 years. This quick mental math helps evaluate investment opportunities.

How does inflation affect my investment?

At 3% inflation, your money loses about half its purchasing power every 24 years. A $1M portfolio in 2026 buys the equivalent of ~$475K in 2050 dollars. This calculator's inflation adjustment shows your real purchasing power so you can plan accordingly.