Investment Calculator
An investment grows by earning returns on both your money and past gains: $10,000 plus $500 a month at 7% a year grows to about $292,465 in 20 years, $162,465 of it growth on $130,000 invested. At 3% inflation, that is $161,931 in today's dollars.
By the Calculators With Steps team · Updated November 10, 2026 · How we check our math
- Total contributions
- $130,000$10,000 start + $120,000 added
- Investment growth
- $162,465
- Value in today's dollars
- $161,931after 3% yearly inflation
- Real (after-inflation) return
- 3.88%per year
- Starting amount
- Contributions
- Growth
Step-by-step working
- Monthly growth rate equivalent to 7% a year: (1 + 0.07)^(1/12) − 1 = 0.00565415
- Starting amount: $10,000.00 × (1 + 0.07)^20 = $38,696.84
- Contributions: $500.00 × ((1 + i)^240 − 1) ÷ i with i = 0.00565415 = $253,768
- Ending balance = $292,465
- In today's dollars: $292,465 ÷ (1 + 0.03)^20 = $161,931
Show year-by-year table
| Year | Added this year | Total contributed | Balance | In today's dollars |
|---|---|---|---|---|
| 1 | $6,000 | $16,000 | $16,890 | $16,398 |
| 2 | $6,000 | $22,000 | $24,263 | $22,870 |
| 3 | $6,000 | $28,000 | $32,151 | $29,423 |
| 4 | $6,000 | $34,000 | $40,592 | $36,065 |
| 5 | $6,000 | $40,000 | $49,623 | $42,806 |
| 6 | $6,000 | $46,000 | $59,287 | $49,652 |
| 7 | $6,000 | $52,000 | $69,627 | $56,614 |
| 8 | $6,000 | $58,000 | $80,692 | $63,699 |
| 9 | $6,000 | $64,000 | $92,530 | $70,917 |
| 10 | $6,000 | $70,000 | $105,197 | $78,277 |
| 11 | $6,000 | $76,000 | $118,751 | $85,788 |
| 12 | $6,000 | $82,000 | $133,254 | $93,462 |
| 13 | $6,000 | $88,000 | $148,772 | $101,307 |
| 14 | $6,000 | $94,000 | $165,376 | $109,333 |
| 15 | $6,000 | $100,000 | $183,143 | $117,552 |
| 16 | $6,000 | $106,000 | $202,153 | $125,975 |
| 17 | $6,000 | $112,000 | $222,494 | $134,612 |
| 18 | $6,000 | $118,000 | $244,258 | $143,476 |
| 19 | $6,000 | $124,000 | $267,547 | $152,578 |
| 20 | $6,000 | $130,000 | $292,465 | $161,931 |
Assumes a steady return with contributions at the end of each period, and ignores fees and taxes. Real markets rise and fall; past returns do not guarantee future results.
How to use the investment calculator
- Starting amount – what you invest today. Enter 0 if you are starting from scratch.
- Contribution and frequency – how much you add each month or each year.
- Expected annual return – the average yearly growth you assume, after fund fees.
- Years to invest – how long until you need the money.
- Annual contribution increase (optional) – raise your contribution each year, for example in line with pay rises.
- Inflation rate (optional) – shows the ending value in today’s dollars. Set it to 0 to skip.
The result shows the ending balance, how much came from your own money and how much from growth, a yearly chart and a table with the balance in both future and today’s dollars.
How the projection is calculated
The calculator converts the annual return R into the monthly rate that compounds to it, i = (1 + R)^(1/12) − 1, then steps through every month: the balance grows by i, and contributions are added at the end of each month (or at the end of each year for annual contributions). With a constant contribution this matches the standard formulas:
FV = P(1 + R)^t + C × [(1 + i)^n − 1] ÷ i
- P = starting amount
- C = contribution per period, n = number of contributions
- R = annual return, i = return per contribution period
- t = years
To express the result in today’s dollars, divide by (1 + inflation)^t.
Worked example
$10,000 to start, $500 a month, 7% a year for 20 years, with 3% inflation:
| Item | Value |
|---|---|
| Starting amount after 20 years | $38,696.84 |
| Total contributed | $130,000 |
| Ending balance | $292,465 |
| Growth from returns | $162,465 |
| In today’s dollars | $161,931 |
| Real return | 3.88% a year |
More than half of the final balance is growth rather than money you put in. Most of it arrives late: the balance passes $105,000 after 10 years and then nearly triples over the next 10.
How the return assumption changes the result
The same $10,000 plus $500 a month over 20 years:
| Annual return | Ending balance | Growth |
|---|---|---|
| 5% | $229,435 | $99,435 |
| 7% | $292,465 | $162,465 |
| 9% | $375,470 | $245,470 |
| 10% | $426,405 | $296,405 |
A few percentage points change the outcome by more than $100,000. Fees work the same way in reverse: a 1% annual fee turns a 7% return into roughly 6%. Low-cost index funds keep more of the return in your account.
Nominal vs. real returns
The ending balance is in future dollars. A dollar in 20 years will buy less than a dollar today, so the calculator also divides by cumulative inflation to show the value in today’s money. In the example, $292,465 in 20 years has the buying power of about $161,931 now. The same idea gives the real return: (1 + 7%) ÷ (1 + 3%) − 1 = 3.88% a year. Planning with real values keeps goals honest. If you need $50,000 a year of today’s spending in retirement, compare that with a today’s-dollars balance, not the larger future-dollar figure. The inflation calculator converts any amount between today and a future year.
Investing tips
- Start with time, then amount. Investing for twenty years instead of ten adds $60,000 of contributions in the example, but nearly triples the ending balance.
- Automate contributions and raise them when your income rises. A 3% yearly increase adds about $65,577 to the 20-year result.
- Use tax-advantaged accounts first. In the U.S., a 401(k) or IRA can shelter growth from tax. The 401(k) calculator includes employer matching.
- Think in real terms. A projection in today’s dollars is easier to plan with. The inflation calculator shows how prices change over time.
- Check past performance properly. To measure what an investment actually returned, use the ROI calculator or the CAGR calculator.
Returns from stocks and bonds are not guaranteed and do not arrive evenly. A projection with a steady return is a planning tool, not a promise.
Investment Calculator: frequently asked questions
How do I calculate investment growth over time?
For a single amount use FV = P × (1 + R)^t. $10,000 growing at 7% a year for 20 years becomes 10,000 × 1.07^20 = $38,696.84. Regular contributions are added with the future value of an annuity, which this calculator does month by month.
How much will I have if I invest $500 a month?
With $10,000 to start and $500 a month at a steady 7% annual return, you would have about $105,197 after 10 years, $292,465 after 20 years and $660,849 after 30 years. Actual returns vary from year to year.
What rate of return should I use?
There is no single right number. Use a figure that matches your mix of stocks, bonds and cash, and test a range. On the example, 5% gives $229,435 after 20 years and 9% gives $375,470, so the assumption matters a lot.
What does the value in today's dollars mean?
It is the future balance divided by cumulative inflation, so you can compare it with prices now. At 3% inflation, $292,465 in 20 years buys about what $161,931 buys today. The real return is (1.07 ÷ 1.03) − 1 = 3.88% a year.
Does increasing my contribution each year help?
Yes. Raising the $500 monthly contribution by 3% a year lifts the 20-year value from $292,465 to about $358,042. The monthly amount reaches $877 in the final year.
Is it better to invest monthly or once a year?
Monthly investing gets money working sooner. $500 a month for 20 years at 7% ends at $292,465, while $6,000 invested at the end of each year ends at $284,670, about $7,795 less.
How long does it take to double an investment?
Divide 72 by the annual return. At 7% the rule of 72 gives about 10.3 years; the exact figure is 10.2 years.
How we checked this page: every figure in the examples and FAQs above is produced by this calculator and verified by automated tests against known answers, and the rules and rates come from the sources below. Last updated . Spotted a problem? Tell us.
Sources and further reading