Investment Calculator
Project how an investment could grow using an initial balance, monthly contribution, expected annual return, and time horizon. For example, $10,000 invested with $500 monthly contributions at 8% annual return for 20 years could grow to over $320,000 with $130,000 in total contributions.
Investment Details
See how your money grows over time.
The S&P 500 has averaged ~7% annually after inflation (1950-2024).
Projected Growth
Compound interest over 20 years.
Balance after 20 years
$300,851
$170,851 in gains on $130,000 contributed
Methodology and limitations
Last reviewed:
Methodology
Projects investment growth by applying an expected annual return as a monthly growth rate and adding recurring monthly contributions.
Limitations
Projection only. It does not model market volatility, taxes, inflation, account fees, advisory fees, or investment suitability.
Official sources
How to Use the Investment Calculator
Project how an investment could grow using an initial balance, monthly contribution, expected annual return, and time horizon. For example, $10,000 invested with $500 monthly contributions at 8% annual return for 20 years could grow to over $320,000 with $130,000 in total contributions.
Method used
This calculator grows the starting balance month by month, adds each monthly contribution, and applies the expected annual return as a monthly growth rate.
Balance after each month = prior balance x (1 + annual return / 12) + monthly contribution
Practical example
Example: start with $10,000, add $500 per month, assume a 7% annual return, and project the balance over 20 years.
- $10,000 initial investment
- $500 monthly contribution
- 7% expected annual return
- 20-year time horizon
The output separates total contributions from estimated gains so the projection is easier to audit.
Assumptions
- Contributions are added monthly.
- The expected return is steady across the full projection.
- Results are nominal and do not adjust for taxes or inflation.
What this includes
- Initial balance, monthly contribution, expected return, and time horizon.
- Final balance, total contributed, estimated gains, and milestone balances.
What this excludes
- Market volatility, tax treatment, fees, inflation, and contribution timing differences.
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Frequently Asked Questions
How does this investment calculator work?
Enter your starting balance, expected annual return, monthly contribution amount, and investment time horizon in years. The calculator converts the annual return to a monthly growth rate, compounds it each month, and adds your contribution at the end of each period. The result shows your projected ending balance, total amount contributed, and estimated investment gains. Milestone balances at key intervals help you visualize growth over time.
Does this include taxes or fees?
No. The projection is before federal and state taxes, capital gains taxes, fund expense ratios, advisory fees, transaction costs, and inflation. Real-world returns are reduced by all of these factors. Tax-advantaged accounts like IRAs and 401(k)s defer or eliminate some taxes, while taxable brokerage accounts may owe taxes on dividends and realized gains annually. Factor in your estimated fee drag and tax bracket for a more realistic projection.
Is the expected return guaranteed?
No. Expected return is an assumption you enter based on historical averages, your asset allocation, or financial planning guidelines. Actual investment returns vary year to year and can be significantly higher, lower, or negative - especially over short periods. Stocks have historically averaged roughly 7% to 10% annually before inflation over long horizons, but any single year can see double-digit losses. This calculator illustrates compound growth math, not a guarantee of future performance.
What is total contributed?
Total contributed is the sum of your initial investment plus every monthly contribution made during the projection period. It represents the money you put in from your own pocket. Estimated gains equal the projected ending balance minus total contributed. Separating contributions from gains helps you see how much of your ending balance came from your savings discipline versus investment growth over the time horizon.
How much will my investments be worth in 20 years?
Your ending balance depends on four inputs: starting amount, monthly contributions, expected annual return, and years invested. Small increases in any variable compound significantly over long horizons. For example, raising monthly contributions from $300 to $500 at 8% over 20 years adds tens of thousands to the final balance. Adjust each input in this calculator to model different scenarios and find a savings rate that matches your financial goals.