Investment Calculator (2026): See How Much Your Money Could Grow
An investment calculator estimates what your money could be worth in the future, based on what you start with, what you add each month, how long you invest and the yearly return you assume. It will not predict the market, but it shows how big the effect of time, contributions and fees can be, which is the part you control.
Below is a free investment calculator you can use right now, followed by a plain-English guide to what the numbers mean, which return to enter, how fees and inflation change the result and where calculators fall short. All examples use my own calculations and are labeled as illustrations.
Use the Free Investment Calculator
Change any number and the estimate updates. The starting values are an example: $5,000 to begin, $300 a month, a 7% yearly return and 20 years.
Free Investment Calculator
Enter your numbers to estimate how an investment could grow. The results update as you type.
Year-by-year table
| Year | Put in | Balance |
|---|
Estimates only, not investment advice or a prediction. Assumes a constant yearly return compounded monthly, contributions at the end of each month, and no taxes. Real returns change every year.
Table of Contents
How an Investment Calculator Works
Most investment calculators use compound growth. Each month your balance earns a return, and the next month that return earns a return too. Your monthly deposits are added on top.
The formula behind the calculator above is:
Balance = Start × (1 + i)n + Monthly × ((1 + i)n − 1) ÷ i
Here, i is your yearly return minus fees, divided by 12, and n is the number of months. It assumes a constant return and deposits at the end of each month.
Take the example in the calculator: $5,000 to start, $300 a month, 7% for 20 years. You put in $77,000 in total, and the estimated balance is $176,472. That means about $99,472 comes from growth, more than the money you contributed. This is why the calculator shows compounding so clearly, and why time matters so much.
What Return Should You Enter?
This is the hardest input, and no calculator can answer it for you. A common starting point is the long-run history of the U.S. stock market. From April 1957 through April 2025, the S&P 500 returned about 10.4% a year with dividends reinvested, or about 6.5% a year after inflation, according to figures cited by SmartAsset from DQYDJ’s S&P 500 return calculator [1].
Those averages hide big swings. The same source notes a return of −18.11% in 2022 followed by 26.29% in 2023, and that it is very rare for the index to land near its average in any one year [1]. A history of strong returns does not guarantee future results.
Run three scenarios, not one
Instead of betting on one return, run a cautious, a middle and an optimistic case. Here is the same $5,000 start and $300 a month over 20 years, with no fees (my calculation):
| Yearly return | Estimated balance | Growth |
|---|---|---|
| 5% | $136,873 | $59,873 |
| 7% | $176,472 | $99,472 |
| 9% | $230,412 | $153,412 |
The range between the cautious and optimistic cases is about $93,500. If your plan only works at the optimistic number, it is fragile. Plan around the lower cases and treat anything above as a bonus. If you hold bonds or cash as well as stocks, your overall return assumption should be lower than a stock-only figure.
Investment Calculator Examples
How time changes the result
Using the same $5,000 start, $300 a month and 7% return (my calculation):
| Time invested | You put in | Estimated balance |
|---|---|---|
| 10 years | $41,000 | $61,974 |
| 20 years | $77,000 | $176,472 |
| 30 years | $113,000 | $406,574 |
Going from 20 to 30 years adds $36,000 of contributions but more than doubles the balance. Most of the growth arrives in the final years, which is why stopping early costs so much.
The cost of waiting
Now take someone who starts from $0 and invests $300 a month until age 65 at the same 7% assumption.
Starting at 35 instead of 25 means contributing $36,000 less, but ending with about $421,000 less. This is an illustration of compounding, not a prediction, and real returns will not be smooth. It is also a reason to start with whatever amount you can afford now rather than waiting for a perfect number.
How Fees Change the Result
Fees reduce your return every year, and the loss compounds along with your gains. In the calculator, enter your fund’s expense ratio plus any advisory fee in the fees box. Here is the same $5,000 start and $300 a month over 30 years at a 7% gross return (my calculation):
| Yearly fees | Estimated balance | Lost to fees |
|---|---|---|
| 0% | $406,574 | $0 |
| 0.10% | $398,241 | $8,333 |
| 0.50% | $366,812 | $39,762 |
| 1.00% | $331,467 | $75,107 |
A 1% fee looks small, but over 30 years it costs about $75,000 in this example. Check the expense ratio of any fund before you buy it, and ask whether an advisor’s fee is charged on top.
Inflation: Nominal vs Today’s Dollars
A balance of $176,472 in 20 years will not buy what $176,472 buys today. That is why the calculator also shows a result in today’s dollars. At a 3% inflation assumption, the $176,472 example is worth about $97,708 in today’s purchasing power. At 3.7%, it is about $85,330.
The latest reading is higher than the 3% example: the Bureau of Labor Statistics reported that consumer prices rose 3.7% over the 12 months ended September 2026 [2]. Inflation changes over time, so use a long-run assumption you are comfortable with, and test a few. If you use the historical figure of about 6.5% a year after inflation instead, you are effectively working in today’s dollars from the start [1].
Taxes and Account Limits
The calculator above does not include taxes. Your real result depends on the account you use and how it is taxed, which is worth learning before you invest. The IRS limits for 2026 reported by InvestmentNews are [3]:
- 401(k) and similar plans: $24,500 employee contribution limit, up $1,000 from 2025.
- Catch-up, age 50 and over: an extra $8,000, and $11,250 for ages 60 to 63.
- IRA: $7,500, plus a $1,100 catch-up for age 50 and over.
If your monthly contribution times 12 is above a limit, the calculator’s result is not realistic for that account. Check the IRS site and your plan for eligibility rules, and consider talking to a tax professional. If you are new to all this, start with our beginner’s guide to investing.
5 Steps to Use an Investment Calculator Well
Step 1: Start with a realistic monthly amount
Enter what you can keep up for years, not your best month. Consistency beats a big number you abandon.
Step 2: Use cautious returns first
Run a low return, a middle return and a high return. Make your plan work at the low one.
Step 3: Add your fees
Enter the real expense ratio of the fund you are considering. A small fee difference is a big dollar difference over decades.
Step 4: Look at today’s dollars
Focus on the inflation-adjusted figure when you compare the result to your goal, such as retirement spending.
Step 5: Revisit once a year
Update the starting amount, contributions and assumptions each year. A calculator is a planning tool, not a one-time answer.
What Any Investment Calculator Cannot Do
- Predict returns. Real markets rise and fall, and a bad year early or late can matter more than the average suggests.
- Include taxes. Interest, dividends and gains can be taxed depending on the account.
- Handle changing contributions. Raises, breaks and lump sums are not modeled unless you rerun it in stages.
- Account for withdrawals. This calculator models saving, not retirement spending.
- Know your goal. It cannot tell you how much you need, only what a plan might produce.
Before you invest at all, make sure you have a cash cushion. Our guide on how to start an emergency fund explains how much to keep in savings so you are not forced to sell investments during a bad month.
Investment Calculator vs Compound Interest and Retirement Calculators
These tools overlap, and the names are used loosely. Knowing the difference helps you pick the right one.
- Investment calculator: projects the future value of an investment from your starting amount, contributions, return and time. Good ones also let you adjust for fees and inflation.
- Compound interest calculator: focuses on how a sum grows at a given rate with compounding. Many include monthly deposits, so the two can give the same answer.
- Retirement calculator: usually works toward a goal, such as how much you might need by a certain age, and often asks about your age, retirement date and expected spending.
- Savings calculator: built for cash accounts, where the rate is an interest rate rather than an investment return.
If you want to see the effect of one decision, such as a lower fee or a higher monthly amount, an investment calculator is the quickest tool. If you want to know whether you are on track for a goal, add a retirement calculator and compare the two.
Other Free Calculators
The U.S. Securities and Exchange Commission offers a free compound interest calculator on Investor.gov. It takes an initial investment, a monthly contribution, the number of years, an estimated rate, a variance range to compare several rates and a compounding frequency [4]. The page does not say whether the results include taxes, fees or inflation, so do not assume they do.
Your brokerage or retirement plan may have its own tool too. Use more than one, compare the assumptions, and trust the one whose assumptions you understand.
Final Thoughts
An investment calculator will not tell you what will happen, but it helps you see which levers matter: how early you start, how much you add, what you pay in fees and what inflation takes back. Use it with cautious assumptions, rerun it each year and treat every result as an estimate.
Try three versions of your own numbers in the calculator above, then write down the monthly amount you can commit to. That one number is the most useful thing the tool can give you.
Frequently Asked Questions
What is an investment calculator?
It is a tool that estimates the future value of your investments from a starting amount, regular contributions, a yearly return and a time period. Many also let you adjust for fees and inflation.
How accurate is an investment calculator?
It is only as accurate as its assumptions. The math is exact, but the return you enter is a guess, and real returns vary from year to year. Treat the result as one possible outcome.
What return should I use in an investment calculator?
The S&P 500 averaged about 10.4% a year from 1957 to April 2025, or about 6.5% after inflation, but yearly results swung widely [1]. Run a cautious, a middle and an optimistic case instead of relying on one number.
Does an investment calculator include taxes and inflation?
It depends on the tool. The one on this page includes fees and an inflation-adjusted figure but not taxes. The SEC’s calculator does not say whether it includes taxes, fees or inflation [4].
How do I calculate investment growth by hand?
Use Balance = Start × (1 + i)n + Monthly × ((1 + i)n − 1) ÷ i, where i is the monthly return and n is the number of months. A spreadsheet can do the same math.
What are the 2026 contribution limits?
For 2026, the 401(k) employee limit is $24,500 and the IRA limit is $7,500, with extra catch-up amounts for people 50 and over [3]. Confirm the details with the IRS.
Sources
- SmartAsset: S&P 500 Average Annual Return (cites DQYDJ data for April 1957 to April 2025; page dated Aug. 23, 2026).
- U.S. Bureau of Labor Statistics: Consumer Price Index news release (September 2026 data, published Oct. 14, 2026).
- InvestmentNews: IRS reveals new 401(k), IRA contribution limits for 2026.
- Investor.gov (U.S. SEC): Compound Interest Calculator.
This calculator and article are for education only, not investment, tax or financial advice. Results are estimates based on the assumptions you enter, and investing involves risk, including the loss of money. Past performance does not guarantee future results.
