What is an Investment Calculator?
An investment calculator shows you how your money can grow over time through the power of compound returns. Enter your starting amount, expected return rate, and regular contributions to see where you could be in 5, 10, or 30 years.
The magic is in compounding: your investment earnings generate their own earnings. A $10,000 investment growing at 8% annually becomes $21,589 in 10 years, $46,609 in 20 years, and $100,626 in 30 years—without adding a single extra dollar.
See Compound Growth
Visualize how your money multiplies over decades
Regular Contributions
See the impact of consistent monthly investing
Time Horizon Impact
Understand why starting early matters so much
Compare Scenarios
See how different return rates affect your outcome
Typical historical returns for reference:
- S&P 500 — ~10% average annual return historically (7% after inflation)
- Bonds — ~4-6% for investment-grade bonds, lower risk
- High-yield savings — ~4-5% APY currently (varies with Fed rates)
- Real estate — ~8-12% including appreciation and rental income
Important: Past Performance
Historical returns don't guarantee future results. Markets fluctuate—some years you'll gain 20%, others you might lose 10%. Use this calculator for planning, but invest in diversified portfolios and think long-term.
How the Math Works
Your final balance is really two separate calculations added together. The starting amount grows on its own as a lump sum, and each recurring deposit grows as its own mini investment for however many periods are left. The calculator runs both period by period, so the figures below match exactly what it returns.
Here is the initial investment, is each contribution, is the annual return as a decimal, is contributions per year, and is the number of years.
Worked Example: $10,000 start, $500/month, 8%, 10 years
Step 1 — grow the starting $10,000
Step 2 — grow the 120 monthly deposits
Final value: $22,196 + $91,473 = $113,669. You put in $70,000 of your own money, so $43,669 of that balance is pure earnings.
Beginning vs End of Period
The Timing dropdown decides whether a deposit is made before or after each month's interest is applied. Depositing at the beginning gives every dollar one extra period of growth. The effect is real but modest. Here is $500 a month at 8% for 20 years with no starting balance.
| Timing setting | Final value | vs. end of period |
|---|---|---|
| Beginning of period | $296,474 | +$1,963 |
| End of period | $294,510 | — |
Does Contribution Frequency Matter?
Less than most people expect. What follows keeps the yearly total identical at $6,000 for 20 years at 8%, only changing how often it is split up. Paying in more often wins because each installment starts compounding sooner, but the gap is small next to the return rate and time horizon.
| Frequency | Per deposit | Final value |
|---|---|---|
| Monthly | $500 × 12 | $294,510 |
| Quarterly | $1,500 × 4 | $290,658 |
| Yearly | $6,000 × 1 | $274,572 |
Why Starting Age Beats Deposit Size
Take three people who each invest $300 a month at 7% until age 65. The only difference is when they start. The one who begins at 25 puts in just $72,000 more than the one who starts at 45, yet ends up with roughly five times as much.
| Start age | Years invested | Total deposited | Value at 65 |
|---|---|---|---|
| 25 | 40 | $144,000 | $787,444 |
| 35 | 30 | $108,000 | $365,991 |
| 45 | 20 | $72,000 | $156,278 |
Taxes and Fees Are Not in These Numbers
The earnings figure the calculator shows is pre-tax and pre-fee. Where you hold the money changes what you actually keep. In a traditional 401(k) or IRA the balance grows untaxed but withdrawals are taxed as income. A Roth IRA is funded with after-tax dollars and qualified withdrawals come out tax-free. A regular taxable brokerage account owes tax on dividends and on gains when you sell, so its real growth trails the on-screen number.
Fee drag: Shaving 1% off the return has an outsized effect over decades. A $10,000 start plus $500 a month for 30 years reaches $854,537 at 8% but only $691,150 at 7%. That single percentage point costs about $163,387. When comparing funds, drop the expense ratio out of your expected return before you calculate.