Investment Calculator
Calculate how your investments grow over time. Enter your own assumed return rate and see projected growth with regular contributions.
For educational purposes only. This calculator does not provide investment advice.
📊 Visual Analysis
What This Calculator Does
The Investment Calculator projects how a portfolio might grow over time using compound returns. It combines an initial lump sum with regular monthly contributions, compounding at a rate you specify. All results are mathematical projections based on your inputs — they do not predict actual future performance or constitute investment advice.
Formula
The calculator combines two compounding formulas:
Lump Sum Growth
Where PV is the initial investment, r is the annual return rate, and n is the total number of months.
Regular Contributions
Where PMT is the monthly contribution. Total future value is the sum of both components.
Note: This assumes a constant return rate applied monthly. Real investment returns vary significantly year to year.
Input Fields Explained
Initial Investment ($)
The starting amount you invest as a lump sum. This could be existing savings, a bonus, or any one-time deposit.
Monthly Contribution ($)
The fixed amount you add each month. Regular contributions benefit from dollar-cost averaging and significantly boost long-term growth. Set to $0 for lump-sum-only projections.
Assumed Annual Return (%)
Your personal assumption about the annualized return rate. This is a modeling input, not a prediction. Test different values to understand sensitivity. Real returns fluctuate and may be negative.
Investment Period (years)
How long you plan to keep the investment. Longer periods allow more compounding but also increase exposure to market volatility.
Example Calculation
Start with $10,000, contribute $500/month, assume 6% annual return, for 20 years.
Total contributions = $10,000 + ($500 × 240) = $130,000
Projected final value ≈ $241,000
Compound growth ≈ $111,000
Assumptions: Uses a fixed 6% return for illustration only. Does not account for taxes, fees, inflation, or volatility. Past performance does not predict future results.
How to Read the Result
The projected total value at the end of the period. This is a mathematical projection, not a guarantee.
The total amount you put in: initial investment plus all monthly contributions.
The difference between final value and contributions — the return generated by compounding.
Common Mistakes
- Assuming a fixed return is realistic. Real investments do not produce steady returns. Markets fluctuate. Sequence of returns matters.
- Overestimating returns. Optimistic assumptions produce impressive projections but may lead to disappointment. Test with conservative rates.
- Ignoring inflation. A dollar in 20 years buys less. Subtract expected inflation from your assumed return to estimate real purchasing power.
- Forgetting taxes and fees. Capital gains taxes, fund fees, and advisory costs reduce your actual return. Even 1-2% annual fees significantly reduce long-term growth.
- Treating projections as promises. Use this calculator for planning and sensitivity analysis, not as a guarantee of outcomes.
Limitations
- Assumes a constant return rate every month — real returns fluctuate significantly
- Does not model sequence-of-returns risk
- Does not account for taxes on investment gains
- Does not deduct fund management fees, advisory fees, or trading costs
- Does not adjust for inflation
- This calculator provides mathematical projections for educational purposes and does not constitute investment advice
Frequently Asked Questions
Does this assume monthly compounding?
Yes. The return rate you enter is treated as an annual figure, converted to a monthly rate for compounding. Real portfolios compound on varying schedules; the difference is usually small compared to the uncertainty in your assumed return rate.
What return rate should I enter?
There is no single correct rate. The return rate is your personal assumption, not a prediction. You can test different scenarios: try conservative and optimistic values to see how your results change. Past market returns do not guarantee future results.
Does this calculator account for inflation?
No. The results are in nominal terms. To estimate real growth, subtract your expected inflation rate from the return rate you enter. For example, if you assume 7% return and 3% inflation, enter 4% to approximate real growth.
What happens if I skip the monthly contribution?
Set the monthly contribution to $0 to calculate growth on a one-time lump sum only. This shows the effect of compound interest without additional deposits.
Are the projected results guaranteed?
No. This calculator shows mathematical projections based on a fixed return rate you provide. Real investments fluctuate and may lose value. The fixed-rate assumption does not reflect volatility, taxes, fees, or sequence-of-returns risk.
How are taxes and fees handled?
They are not. This calculator shows gross growth before any taxes on gains, fund fees, or trading costs. Your actual return will be lower after expenses.
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Educational Disclaimer
This calculator is for educational and informational purposes only. It does not provide investment, financial, tax, or legal advice. The results are based on the inputs and assumptions you provide and may not reflect real market conditions, fees, taxes, or risks. Always do your own research or consult a qualified professional before making financial decisions.