Investment Calculator
Find out what your money could become. This investment calculator projects the future value of a lump sum plus regular monthly contributions, so you can see the real impact of compounding before you commit a single dollar.
- Instant results with no sign-up, email, or spreadsheet required
- See your gross growth versus the amount you actually contributed
- Model monthly, quarterly, or annual compounding side by side
- Built for US investors planning brokerage, IRA, or 401(k) growth
Run Your Numbers
Enter your starting balance, what you plan to add each month, an expected annual return, and your time horizon. The investment calculator below does the rest.
Example Calculations
Curious what realistic numbers look like before you type anything in? Here are four common scenarios run through this investment calculator, using monthly compounding.
| Total contributed | $53,000 |
| Investment growth | $71,379 |
| Total contributed | $100,000 |
| Investment growth | $106,088 |
| Total contributed | $115,000 |
| Investment growth | $204,522 |
| Total contributed | $170,000 |
| Investment growth | $103,568 |
Notice how, in the $25,000 example, total growth actually exceeds total contributions. That’s the core argument for starting early: time invested matters more than the size of any single deposit. If you’d rather model a single lump sum without monthly additions, the Compound Interest Calculator isolates that calculation for you.
How This Investment Calculator Works
This investment growth calculator combines two well-known financial formulas: compound interest on your starting balance, and a future-value-of-annuity calculation for your recurring monthly contributions. Rather than using a single annual formula, the calculator simulates your account month by month, which keeps the projection accurate even when you switch between monthly, quarterly, or annual compounding.
repeated for every compounding period across your timeline
In plain terms: each month, your contribution is added to a holding pool. When a compounding period closes (monthly, quarterly, or annually, depending on what you select), the pool and your existing balance both earn the period’s return together. That return is then folded permanently into your balance, and the process repeats for every remaining period.
Assumptions Used
- Your annual return rate stays constant for the full timeline — real markets fluctuate year to year, so treat this as an average, not a guarantee.
- Monthly contributions are added at a fixed amount; the calculator doesn’t account for raises, bonuses, or contribution increases over time.
- Returns are pre-tax and pre-fee. Brokerage fees, fund expense ratios, and capital gains tax can all reduce your real-world net income from investing.
- Contributions made during a compounding period don’t earn returns until that period closes, which slightly understates growth for monthly contributions under quarterly or annual compounding.
Because of these assumptions, treat your result as an estimate, not a financial promise. Markets are unpredictable, and even small changes to your expected annual return can swing your future value by tens of thousands of dollars over a multi-decade timeline. That’s exactly why this tool exists: to let you stress-test different rates and contribution levels in seconds, instead of guessing.
Understanding Your Investment Calculator Results
When you run the numbers, you’ll see three figures: future value, total contributed, and total growth. The future value is your full projected portfolio balance at the end of your chosen timeline. Total contributed is simply your initial investment plus every monthly deposit added up — money that came directly out of your pocket. Total growth is the difference between the two, and it represents money your portfolio earned on its own, without you lifting a finger.
This distinction matters more than most people realize. A common mistake when evaluating any income calculator or investment calculator is focusing only on the final number without separating contribution from return. Two portfolios can both end up worth $300,000, but one might be 80% your own money while the other is 60% market growth. The second portfolio did far more of the work for you, which is the entire point of investing early and staying consistent.
It also helps to think about your monthly contribution the same way you’d think about monthly income on a budget. Just as a paycheck builds your gross income over a year, a recurring investment builds your portfolio over a decade or more. The earlier those contributions start compounding, the less your net income needs to stretch later in life to hit the same retirement goal — because your money has been doing part of the saving for you the whole time.
If you’re trying to connect this projection back to your paycheck, the Salary Calculator and Take Home Pay Calculator can help you figure out exactly how much room your monthly budget has for new contributions, after taxes and deductions are accounted for. Many people increase their monthly investment amount the moment they see, in dollar terms, how much that extra $100 or $200 a month actually compounds into over 20 or 30 years.
Finally, remember that an investment calculator like this one is a planning tool, not a prediction engine. Use it to compare scenarios — a higher monthly contribution versus a higher assumed return, a shorter timeline versus a longer one — rather than to lock in a single expected outcome. Run it again whenever your income, goals, or risk tolerance change.
Investment Calculator FAQ
How accurate is this investment calculator?
It’s accurate as a mathematical projection based on the numbers you enter, but it can’t predict real market behavior. Actual returns vary year to year, so use a conservative rate (5–7%) for cautious planning and a higher rate only to see a best-case scenario.
Is this calculator free to use?
Yes. This investment calculator is completely free, with no account, email address, or download required. You can run unlimited scenarios and adjust your inputs as many times as you like.
Does this calculator account for taxes or fees?
No. Results are shown pre-tax and pre-fee. Brokerage commissions, fund expense ratios, and capital gains taxes on withdrawal will all reduce your actual take-home growth, so treat the displayed future value as a gross estimate rather than a net one.
What’s a realistic annual return rate to use?
The S&P 500 has historically averaged roughly 7–10% annually before inflation over long periods, though any single year can vary widely. Many planners use 6–7% for conservative, inflation-adjusted projections, while more aggressive estimates use 8–10%.
Can I use this for retirement account projections like a 401(k) or IRA?
Yes, the math is the same whether your money sits in a taxable brokerage account, a 401(k), or an IRA. For a projection built specifically around retirement age and withdrawal planning, try the Retirement Calculator.
How does compounding frequency change my results?
More frequent compounding (monthly versus annually) lets your returns start earning their own returns sooner, which produces a slightly higher future value over long timelines. The difference is usually modest compared to changing your contribution amount or your time horizon.
Should I increase my monthly contribution over time?
This calculator assumes a fixed monthly contribution, but in practice, increasing your contribution as your income grows — even by a small percentage each year — can meaningfully boost your future value. Re-run the calculator periodically with updated numbers to see the impact.
How often should I update my investment estimate?
Revisit your numbers any time your income, savings rate, or goals change, and at minimum once a year. Markets shift, contribution limits change, and your own financial picture evolves, so an annual checkup keeps your plan realistic.
What’s the difference between this and a compound interest calculator?
This investment calculator includes recurring monthly contributions in addition to your initial lump sum. If you only want to project a single upfront amount with no additional deposits, the dedicated Compound Interest Calculator may be simpler to use.
Can I calculate how much I need to invest monthly to hit a goal?
This version solves forward from your inputs to a future value. To work backward from a target goal — for example, “I want $500,000 by age 60” — try adjusting your monthly contribution and rerunning the calculator until the future value matches your target, or use the FIRE Calculator for goal-based planning.
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This investment calculator is provided for educational and planning purposes only and does not constitute financial advice. Results are estimates based on the assumptions you enter and do not account for taxes, fees, or market volatility. Consult a licensed financial advisor before making investment decisions.