Formulas and 2026 figures checked & updated: September 2026
Investment Details
Include fund and advisory fees once; leave zero if your return is already after fees.
Projected Results
Final Portfolio Value
$343,778
How to Use the Investment Return Calculator: Contributions, Fees and Inflation
- Enter your starting investment — the lump sum you're investing today, or $0 if you're starting from scratch.
- Enter how much you'll contribute each month going forward.
- Set an assumed annual return and annual investment fee. Fees reduce the return before monthly compounding; taxes are excluded.
- Enter the number of years you plan to stay invested before you'll need the money.
- Enter an inflation rate and toggle inflation-adjusted if you want the result expressed in today's purchasing power.
- Read your projected balance and contributions versus growth. With no fees, $10,000 plus $500 at each month end for 20 years at 8% grows to about $343,778; $130,000 is contributed.
What This Calculator Does
The Investment Return Calculator projects how a brokerage portfolio grows over time, combining an initial lump-sum investment with regular monthly contributions and a compounding annual return. It's built for long-term planning — retirement, a house down payment, or general wealth building outside of tax-advantaged accounts.
The model uses your starting investment, monthly contribution, annual return, annual fee, investment period and inflation. It compounds monthly after subtracting fees from the annual return. No asset allocation or historical return is assumed to predict your results.
Use this calculator to check whether your current savings rate is on pace for retirement or another long-term goal, to compare the long-run impact of a higher versus lower expected return or monthly contribution, or to see how sensitive a projection is to inflation before relying on a big future number. Toggle 'inflation-adjusted' to see results in today's purchasing power — a portfolio that grows to $500,000 in 20 years feels very different once inflation is factored in. It's also useful alongside a target withdrawal rate, since many retirement plans use roughly a 4% initial withdrawal rate as a starting point to translate a projected portfolio value into an estimate of sustainable annual income. Running the numbers at a few different assumed return rates side by side is a simple way to stress-test a plan before committing to it.
Formula
FV = PV(1+r)^n + PMT × [((1+r)^n − 1) / r]Future value combines growth on your initial investment with growth on a stream of monthly contributions, both compounding monthly. For today’s purchasing power, divide the nominal final value by (1 + annual inflation)^years. When r is zero, FV = PV + PMT × n.
- PVInitial investment (lump sum)
- PMTMonthly contribution amount
- rMonthly return after fees: (annual return − annual fee) ÷ 100 ÷ 12
- nTotal number of months invested
Examples
Example 1: $10,000 start, $500/month for 20 years at 8%
Initial investment of $10,000 plus $500/month for 20 years (240 months) at an 8% nominal annual return.
Final portfolio ≈ $343,778, with $130,000 contributed and $213,778 of growth. Assumes no fees and month-end contributions.
Example 2: Same scenario, inflation-adjusted at 3%
Same nominal contributions and no fees, with annual inflation of 3%. Divide the $343,778 ending balance by 1.03^20.
Ending purchasing power ≈ $190,342 in today’s dollars. Future monthly contributions are fixed at $500, so their purchasing power also falls over time.
Example 3: The Rule of 72 in action
A $50,000 investment with no further contributions, growing at 8% per year, with no withdrawals.
Using the Rule of 72 (72 ÷ 8 = 9), the investment roughly doubles to $100,000 in about 9 years and doubles again to $200,000 by year 18.
Key Terms Explained
- Compound Interest
- Interest earned on both your original balance and previously earned interest, so growth accelerates the longer money stays invested.
- Real Return
- An investment's return after subtracting inflation — what your money actually gains in purchasing power.
- Inflation
- The gradual rise in prices that erodes purchasing power, so a dollar buys less over time.
- Principal
- The original amount borrowed or invested, before interest. Each loan payment is split between paying down principal and paying interest.
- Safe Withdrawal Rate
- The share of a portfolio you can withdraw each year with low risk of running out — traditionally around 4% (the “4% rule”).
Continue Your Financial Planning
Sources and methodology
How SmartRates checks calculations · About the editorial team
Methodology
Contributions arrive at each month end and stay fixed in nominal dollars. Monthly return = (annual return − annual fee) ÷ 12. Future purchasing power = nominal ending balance ÷ (1 + annual inflation)^years. In the real view, contributions are discounted separately at their deposit dates, and growth is the residual. Fees use a simplified annual percentage-point deduction. Taxes, withdrawals and variable market returns are excluded.
Frequently Asked Questions
Which return should I enter?+
Use an assumption appropriate to your investments and test a lower-return scenario too. The default 8% is an illustration, not a forecast. Returns can be negative and this constant-rate model does not simulate market volatility.
What is the Rule of 72?+
Divide 72 by your annual return rate to estimate how many years it takes to double your money. At 8% per year, money doubles in roughly 9 years (72 ÷ 8). At 6%, it takes 12 years.
How does compound interest work in investing?+
Returns compound when gains are reinvested, earning future returns on top of prior gains. A $10,000 investment at 8% grows to $10,800 after year one. In year two, you earn 8% on $10,800 (not just $10,000), giving $11,664 — the extra $64 is compounding at work.
Are contributions made at the start or end of the month?+
At month end. Contributions remain fixed in nominal dollars; they do not rise automatically with inflation. Start-of-month contributions would receive one extra month of growth.
How is the inflation-adjusted rate calculated?+
First convert the monthly return after fees into an effective annual return. Then real annual return = (1 + effective annual return) / (1 + inflation) − 1, using decimal rates. The final portfolio is discounted by cumulative inflation. Subtracting inflation from an annual rate is only an approximation.
Is it better to invest a lump sum or dollar-cost average monthly?+
Historically, investing a lump sum immediately has outperformed dollar-cost averaging — spreading the same amount across several months — in a majority of historical periods, simply because markets trend upward over time and more money is invested for longer. However, dollar-cost averaging can reduce the risk and regret of investing a large sum right before a downturn, and it's the natural approach for anyone investing from ongoing income rather than a windfall.
Can I save my results?+
Yes. Use “Save results” to store a snapshot. Without an account it remains in this browser. If you log in, saved scenarios sync securely to your SmartRates account so they are available on your other devices.
How do I share my calculation?+
Click “Share” in the toolbar to copy a link (or open your device’s share sheet). The link encodes your exact inputs, so whoever opens it sees the calculator pre-filled with the same numbers and the same result.
Can I email my calculator results?+
Yes. Click “Email results” to open your default email application with the current inputs, results, and calculator link already included. Review the message and choose the recipient before sending.
Can I export or print my results as a PDF?+
Yes. Click “Export PDF” to open a clean, printable summary of your inputs and results that you can save as a PDF or print. It includes a timestamp and a link back to the calculator.
How accurate are the calculator results?+
The arithmetic follows the formula and assumptions documented on this page. The result is still an estimate because actual rates, fees, taxes, timing conventions, eligibility rules, and provider calculations can differ. Use figures from your official quote, statement, contract, or tax form before making a financial decision.
Which inputs have the biggest effect on the result?+
Rate, time, starting balance, recurring payments or contributions, and fees usually have the largest effects. Change one input at a time to create a conservative, expected, and optimistic scenario instead of relying on a single forecast.
Are taxes, fees, and inflation included?+
Only when they appear as an input or are explicitly described in the methodology. Do not assume an omitted cost is zero. Review the formula and methodology sections to see exactly what is included before comparing the result with an outside quote.
Can this calculator predict future rates or returns?+
No. A calculator projects the assumptions entered; it cannot predict market returns, inflation, variable interest rates, tax-law changes, or provider decisions. Rerun the calculation with several assumptions to understand the range of possible outcomes.
Why might my lender, bank, broker, or tax software show a different result?+
Professional systems may use daily timing, transaction dates, compounding conventions, rounding rules, account-specific fees, credits, eligibility details, or regulations that a general-purpose calculator cannot know. A small difference can be rounding; a large difference usually means an assumption or included cost is different.
Disclaimer: Calculations are for informational purposes only and do not constitute professional financial advice. Please consult with a certified professional before making financial decisions.