Calculate Investment Growth
How This Calculator Works
The Investment Return Calculator projects how an initial deposit plus regular monthly contributions grow over time using compound interest. It applies this formula each month:
FV = P × (1 + r)^n + C × [((1 + r)^n − 1) / r]
Where:
- P = initial investment (your starting amount)
- C = contribution per period (monthly amount added)
- r = periodic rate (annual rate ÷ 12)
- n = total compounding periods (years × 12)
All calculations run entirely in your browser. No data is sent to any server.
How to Use It
- Enter your initial investment — the lump sum you start with (can be $0)
- Set a monthly contribution — the amount you plan to add each month
- Choose an expected annual return — the average yearly growth rate you want to model
- Pick a time horizon — how many years you want to project
The results update automatically: future value, total contributions, interest earned, and a year-by-year table.
Understanding Compound Growth
Compound growth means your returns generate their own returns. Each period, interest is calculated on the entire balance — including all previously earned interest. Over long time horizons, this creates exponential growth rather than linear growth.
Why Regular Contributions Matter
Each contribution you make starts earning compound returns from the moment it enters the account. Over time, the accumulated contributions and their earned returns can exceed the growth on your initial deposit alone.
Here is an example showing $10,000 initial investment at 7% annual return, compounded monthly:
- Without contributions: $10,000 grows to ~$40,387 in 20 years
- With $200/month: The total reaches ~$144,478 in 20 years — of which $58,000 is deposits and ~$86,478 is earned interest
- With $500/month: The total reaches ~$293,103 in 20 years — of which $130,000 is deposits and ~$163,103 is earned interest
In each case, a significant portion of the final balance is interest earned on contributions — not the contributions themselves.
The Impact of Time
Time is the most powerful variable in compound growth. Starting 10 years earlier with smaller amounts can produce a larger result than starting later with larger amounts.
- $200/month for 30 years at 7% → ~$243,994 (total contributed: $72,000)
- $400/month for 20 years at 7% → ~$208,956 (total contributed: $96,000)
The first scenario contributes $24,000 less but ends up with $35,000 more — because the earlier contributions had longer to compound.
Choosing a Return Rate
The return rate you enter significantly affects the projection. Common reference points:
- 2–3%: Approximate range for high-yield savings accounts or short-term bonds
- 5–6%: Moderate estimate sometimes used for balanced or diversified portfolios
- 7–10%: Historical average range for broad stock market indices (before inflation)
These are reference points, not recommendations. Actual returns vary year to year and are never guaranteed. Past performance does not predict future results. For guidance on expected returns for a specific investment, consult a qualified financial professional.
Adjusting for Inflation
This calculator shows nominal values — it does not subtract inflation. To approximate inflation-adjusted ("real") growth, reduce the annual return by an estimated inflation rate before entering it. For example, if you expect 7% nominal returns and 3% inflation, enter 4% to see approximate real purchasing power growth.
For a dedicated inflation projection, see the inflation calculator.
Related Formulas and Tools
- Compound Interest Calculator — model compounding with adjustable frequency (daily, monthly, quarterly, annually)
- Savings Goal Calculator — find out how much to save monthly to reach a target amount
- ROI Calculator — calculate return on investment as a percentage
- How Compound Interest Works — in-depth guide with formulas, examples, Rule of 72, and common mistakes
Frequently Asked Questions
How do I calculate investment returns with monthly contributions?
The future value formula combines two parts: compound growth on the initial amount, and compound growth on each contribution. The formula is FV = P×(1+r)^n + C×[((1+r)^n − 1)/r], where P is the starting amount, C is the contribution per period, r is the periodic rate, and n is the total periods. This calculator handles the math for you — just enter your numbers and see the projected result.
How much will $10,000 invested for 20 years be worth?
At 7% compounded monthly with no additional contributions, $10,000 grows to approximately $40,387. Adding $500/month raises the projected total to roughly $293,103. The exact result depends on the return rate and contribution amount. Use the calculator above to model your specific scenario.
What annual return rate should I enter?
That depends on what you're modeling. Historical averages for broad stock indices have been roughly 7–10% annually before inflation, but past results do not guarantee future performance. For conservative projections, some people use 5–7%. This calculator shows hypothetical projections, not predictions. Consult a financial professional for guidance on expected returns for specific investments.
Does this calculator account for inflation?
No. Results are shown in nominal (unadjusted) terms. To approximate inflation-adjusted growth, subtract an estimated inflation rate from your expected return before entering it. For example, enter 4% instead of 7% to approximate the impact of 3% annual inflation. For dedicated inflation projections, use the inflation calculator.
Does this calculator account for taxes?
No. All results are before taxes. In practice, investment gains may be subject to capital gains tax, dividend tax, or income tax depending on the account type and jurisdiction. Tax-advantaged accounts (like IRAs or ISAs) may reduce or defer the tax impact. This calculator does not model after-tax scenarios.
What's the difference between this and a compound interest calculator?
Both use the same compound growth math. A compound interest calculator typically focuses on savings accounts with a fixed interest rate and adjustable compounding frequency. This investment return calculator is designed for longer-term growth projections that include regular monthly contributions, making it useful for modeling retirement savings, education funds, or general wealth building scenarios.
How much do monthly contributions matter compared to the initial investment?
Over long periods, consistent contributions often have a larger impact than the starting amount. For example, $10,000 at 7% for 30 years grows to ~$81,165 on its own. Adding $200/month turns that into ~$323,388 — the contributions and their compound growth add over $240,000. The longer the time horizon, the more powerful contributions become.
Is my data sent to a server?
No. All calculations happen locally in your browser using JavaScript. No financial data is transmitted, stored, or logged by this tool. You can verify this in your browser's developer tools (Network tab). The calculator also works offline after the page loads.
What This Calculator Does Not Do
- It does not account for taxes on gains or contributions
- It does not adjust for inflation (see inflation calculator)
- It assumes a fixed annual return — actual returns fluctuate year to year
- It assumes contributions are made at the same amount every month
- It does not model fees, commissions, or expense ratios
- It does not provide financial, investment, or tax advice
This tool is educational. It demonstrates how compound growth works mathematically. For decisions about investments or savings strategies, consult a qualified financial professional.
Privacy & Limitations
- All calculations run entirely in your browser -- nothing is sent to any server.
- Results are estimates for planning purposes and should not replace professional financial advice.
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Investment Return Calculator FAQ
How do I calculate investment returns with monthly contributions?
Use the future value formula: FV = P×(1+r)^n + C×[((1+r)^n − 1)/r], where P is your initial investment, r is the periodic rate, n is total periods, and C is the contribution per period. This calculator handles the math automatically — enter your initial amount, monthly contribution, expected annual return, and time horizon to see the projected result.
How much will $10,000 invested for 20 years be worth?
At a 7% annual return compounded monthly, $10,000 grows to approximately $40,387 in 20 years without additional contributions. With $500/month added, the projected total reaches approximately $293,103. The actual result depends on the return rate and whether contributions are made.
What annual return should I use in the calculator?
That depends on your scenario. Historically, diversified stock markets have averaged roughly 7–10% annually before inflation, but past returns do not predict future results. For conservative estimates, many people use 6–7%. This calculator shows hypothetical projections — actual returns vary year to year and are never guaranteed.
Does this calculator account for inflation?
No. This calculator shows nominal (unadjusted) future values. To estimate real purchasing power, subtract an estimated inflation rate from your expected return before entering it. For example, entering 4% instead of 7% approximates a 3% inflation adjustment.
Does this calculator account for taxes?
No. All results are before taxes. In practice, investment gains may be subject to capital gains tax, dividend tax, or income tax depending on the account type and jurisdiction. Tax-advantaged accounts may defer or reduce the tax impact.
What is the difference between this and a compound interest calculator?
Both use the compound growth formula. A compound interest calculator typically focuses on savings accounts with a fixed interest rate. This investment return calculator is designed for longer-term growth projections that include regular contributions, making it useful for modeling retirement savings, education funds, or general wealth accumulation over time.
How much do monthly contributions matter compared to the initial investment?
Over long time horizons, regular monthly contributions often have a larger impact than the initial amount. For example, $10,000 invested at 7% for 30 years grows to about $81,165. Adding just $200/month turns that into approximately $323,388. The contributions themselves total $72,000, but they earn compound growth of their own.
Is my data sent to a server?
No. All calculations happen locally in your browser using JavaScript. No financial data is transmitted, stored, or logged. You can use this calculator offline after the page loads.