Investment Calculator
Project the future value of any investment with regular contributions. See three return scenarios (expected, optimistic, pessimistic) and a breakdown of your contributions vs. market returns.
Investment Calculator
Results update instantly as you type
Enter Values
Pessimistic Scenario (−2% = 6.0%)
$1.03M
Contribution: $500/week for 20 years
Monthly equivalent: $2,167/mo
Scenario Comparison
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Growth Over Time — 3 Scenarios
Your Contributions vs. Market Returns at Year 20
Pessimistic
$1.03M
6.0%/yr
Expected
$1.33M
8.0%/yr
Optimistic
$1.72M
10.0%/yr
The Formula
Future ValueThe value of an asset or investment at a specified date in the future, accounting for growth or interest. combines the growth of the initial lump sum with the future value of recurring contributions, all compounded monthly. The first term grows the starting balance, while the second term captures the effect of regular investing over time.
Variable Definitions
Future Value
The total portfolio value at the end of the investment period, including all contributions and compounded returns.
Starting Amount
The initial lump sum invested. Can be set to $0 if you are starting with no existing investments.
Monthly Contribution
The regular contribution amount converted to a monthly equivalent regardless of whether you contribute weekly, monthly, or annually.
Monthly Return
The expected annual return divided by 12. Historical S&P 500 average return is approximately 10% nominal (about 0.83% monthly) or 7% inflation-adjusted.
Months
The total investment period in months, calculated as years multiplied by 12.
How to Use This Calculator
- 1
Enter your starting investment amount (can be $0 if you are starting from scratch with no existing portfolio).
- 2
Enter your regular contribution amount and select whether you invest weekly, monthly, or annually.
- 3
Enter the number of years you plan to invest — longer time horizons dramatically amplify the power of compounding.
- 4
Set your expected annual return and return variance to model best-case, worst-case, and expected scenarios for realistic planning.
Common Applications
- Project the future value of an investment portfolio with recurring contributions to see how consistent investing grows wealth over time.
- Model optimistic, expected, and pessimistic scenarios using the variance feature to understand the full range of potential retirement outcomes.
- Visualize the tipping point where investment returns exceed your own contributions as the dominant source of portfolio growth.
Your contributions grow linearly while compounding investment returns grow exponentially - over decades, market returns typically contribute 70%+ of your final portfolio
Understanding the Concept
This calculator models a realistic investment portfolio with recurring contributions over time. The variance feature is key: no investment returns exactly the same amount every year. Seeing the full range of outcomes from pessimistic to optimistic helps set realistic expectations and prevents overconfidence in any single projection. The bar chart below shows how much of your final value comes from your actual contributions versus market returns. For long time horizons of 20-30 years, the market typically does most of the work — investment returns often account for 70% or more of the final balance, with your own contributions making up the rest. This is the core insight that motivates consistent, long-term investing.
Frequently Asked Questions
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