Expected Investment Returns: How to Estimate Them Honestly
Quick answer: Use future value = start × (1 + return)^years, plus the growth on each monthly deposit (the spreadsheet FV function does this). Run a low, middle and high return, subtract fees and inflation, and plan around the low result. No one can know your real future return in advance.↗ Share on X
You can estimate your expected investment return with one simple formula: future value = what you put in × (1 + yearly return) ^ number of years, plus the growth on each new deposit. The hard part is not the math. It is picking an honest return number. A good habit is to run three versions — a low, a middle and a high return — then subtract fees and inflation, and plan your life around the low one. Nobody can tell you your real future return in advance, so the goal is a range, not a promise.
This page walks you through it step by step, with worked examples you can copy into a phone calculator or a free spreadsheet.
What does "expected return" actually mean?
Target-Date Funds Explained: How the Year Picks Your Mix →
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Capital Gains Tax When Selling Index Funds in Retirement →Expected return is your best guess of how much an investment will grow per year, on average, over a long time. It is written as a percentage, like 5% per year.
Three things to keep in mind:
1. It is an average, not a yearly pay rate. A fund that averages 6% might go up 20% one year and down 15% the next.
2. It is not a promise. Stocks and stock funds can lose money, sometimes for several years in a row.
3. Past results do not lock in future results. Long-run history is a useful guide for setting assumptions, but it is not a contract.
Savings accounts and certificates of deposit (CDs) are different. They pay a stated interest rate. For those, your "expected return" is simply the rate the bank shows you, which may change over time on a savings account.
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Which numbers do you need before you calculate?
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This content is informational and is not investment advice or financial consulting.
Gather these five inputs first. Write them down.
| Input | What it means | Example |
|---|---|---|
| Starting amount | Money you invest on day one | $1,000 |
| Monthly deposit | What you add every month | $200 |
| Years | How long you leave it invested | 20 |
| Yearly return (before fees) | Your guess, in three versions | 3%, 5%, 7% |
| Yearly costs | Fund fees (expense ratio) plus any advisor fee | 0.10% to 1.5% |
You can find the expense ratio — the yearly fee a fund charges, shown as a percentage — on the fund's page at your brokerage. An advisor fee, if you have one, is on your agreement or statement.
How do you calculate it step by step?
How to Pick a Cheap Index Fund for Your First 401(k) or IRA →
How to Calculate Your Net Worth Before You Start Investing →
Should You Turn On Dividend Reinvestment in Your Index Fund? →Step 1: Pick three return assumptions
Don't use one number. Use three:
- Low: a cautious number. If you are mostly in bonds or savings, this might be close to what those pay today.
- Middle: your realistic planning number.
- High: a good-case number. Do not build your budget on this one.
The examples below use 3%, 5% and 7% simply to show how the math works. They are not a forecast for any fund.
Step 2: Subtract yearly costs
Take your return assumption and subtract fees. If you assume 6% and pay 1% in fees, use 5%.
This step matters more than people think. Here is $10,000 left alone for 30 years:
| Yearly return after fees | Value after 30 years |
|---|---|
| 6% | about $57,400 |
| 5% | about $43,200 |
One percentage point of yearly cost changed the result by roughly $14,200. Same money, same years.
Step 3: Grow your starting amount
Formula: Start × (1 + r) ^ years
Example: $1,000 at 5% for 20 years.
1.05 raised to the 20th power is about 2.653.
$1,000 × 2.653 = about $2,653.
On a phone calculator, type 1.05, then the x^y key, then 20.
Step 4: Grow your monthly deposits
Monthly deposits each grow for a different amount of time, so they use a second formula:
Deposit × [((1 + m) ^ months − 1) ÷ m], where m = yearly return ÷ 12.
That looks scary, but a spreadsheet does it for you. In Google Sheets or Excel, type:
`=FV(5%/12, 240, -200, -1000)`
That means: 5% yearly return split into months, 240 months (20 years), $200 per month, $1,000 to start. The minus signs just mean "money going in." The answer is about $84,900.
Step 5: Put your three versions side by side
Here is $200 per month for 20 years, with no starting amount, at three returns (monthly compounding):
| Yearly return after fees | You put in | Estimated value | Growth part |
|---|---|---|---|
| 3% | $48,000 | about $65,700 | about $17,700 |
| 5% | $48,000 | about $82,200 | about $34,200 |
| 7% | $48,000 | about $104,200 | about $56,200 |
Notice that the money you deposit ($48,000) is the same in every row. Only the growth changes. Your savings habit is the part you control.
Step 6: Adjust for inflation
Inflation means prices rise over time, so $82,000 in 20 years will buy less than $82,000 buys today.
A simple shortcut: real return ≈ return after fees − expected inflation.
If you expect 5% after fees and assume prices rise about 2.5% a year, plan with roughly 2.5% to see the result in today's dollars. Run the `FV` formula again with that lower number. The answer tells you what your future balance may feel like in today's buying power.
Is there a quick way to check the math in your head?
Yes. The Rule of 72 tells you about how many years it takes money to double.
72 ÷ yearly return = years to double
- At 3%: about 24 years
- At 6%: about 12 years
- At 9%: about 8 years
It is not exact, but if your spreadsheet says your money will double in 5 years at 4%, you know something is wrong.
What mistakes make return estimates too rosy?
These are the errors that lead people to save too little:
1. Using only the best-case number. Plan with the low or middle number. Treat anything above that as a bonus.
2. Forgetting fees. A fund fee plus an advisor fee can easily add up to 1% or more per year.
3. Ignoring inflation. A big future number can look exciting and still buy less than you expect.
4. Forgetting taxes. In a regular brokerage account, you may owe tax on dividends and on gains when you sell. Accounts like a 401(k) or IRA have different tax rules. Check the rules for your own situation.
5. Assuming smooth growth. Real balances jump up and down. If you will need the money in less than about five years, a drop right before you need it can hurt. Shorter goals usually call for safer places, like high-yield savings or CDs.
6. Mixing up "return" and "yield." A fund's yield is just the income it pays out. Total return also includes price changes, up or down.
How should your time frame change the estimate?
The longer the money stays invested, the more a small change in return matters — and the more time you have to ride out bad years.
| When you need the money | What usually makes sense to plan with |
|---|---|
| Less than 2 years | The stated rate of a savings account or CD |
| 2 to 5 years | A cautious, low number; expect possible ups and downs |
| More than 5 years | A range (low, middle, high), revisited every year |
When should you talk to a professional?
A calculator is fine for a first estimate. Get help from a licensed professional — for example, a fee-only financial planner who is paid by you and not by product commissions — if:
- you are planning for retirement and need to know how much you can safely withdraw each year;
- you have debt with high interest, like credit cards, and are unsure whether to invest or pay it down first;
- you are dealing with an inheritance, a home sale or a large lump sum;
- your taxes are complicated, or you are self-employed.
This article explains how the math works. It is not personal investment advice, and no estimate here predicts what any specific fund will do.
What should you do next?
Open a free spreadsheet today and type `=FV(r/12, years*12, -monthly, -start)` three times — once each for a low, a middle and a high return, after subtracting your fund's expense ratio. Then run the low version again with inflation subtracted. Use that cautious number to decide how much to save each month, and set a calendar reminder to redo the calculation once a year with your real balance.
FAQ
What return should I assume when planning my investments?
Use a range instead of one number: a cautious low, a realistic middle and a good-case high. Subtract fund and advisor fees, and build your budget on the low or middle number.
How do I calculate investment growth in a spreadsheet?
Type =FV(yearly return/12, years*12, -monthly deposit, -starting amount). For example, =FV(5%/12, 240, -200, -1000) estimates about $84,900 after 20 years.
How much do fees really change my returns?
A lot over long periods. $10,000 for 30 years grows to about $57,400 at 6% but only about $43,200 at 5%, so one percentage point of yearly cost changed the result by roughly $14,200.
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Educational content, not personalized financial advice. Sources cited where applicable.