What is index investing?
An index is a list of companies that together stand for part of the market. The S&P 500 is 500 of the largest US companies; the Nasdaq Composite is the thousands of companies listed on the Nasdaq exchange, with a large share in technology.
An index fund is a mutual fund or ETF that tries to match an index by owning the same companies. Instead of betting on a few stocks, you own a small slice of hundreds or thousands at once. Because nobody is paid to pick stocks, index funds are often cheaper than other funds, though not always, so check the fee before you buy.
How this calculator works
It doesn’t guess or assume an average return. It replays what the index actually did, month by month, using historical levels (the average of each month’s daily closes). Your starting amount goes in on the start month, each monthly amount goes in at the following month’s level, and every month your balance rises or falls with the index.
For the S&P 500 it can also add the dividends the companies paid and reinvest them, which is how a fund investor who reinvests would have done. We don’t have dividend history for the Nasdaq Composite, so its results are price only.
It can also adjust for inflation, the general rise in prices. A dollar invested in 2006 bought more than a dollar does now, so with “Inflation: Adjusted” every amount is converted into dollars of your end month using the Consumer Price Index. The final value stays the same, but what you put in counts for more, and the gain shows how much more you could actually buy.
The results include the bad years as well as the good ones. The “biggest fall along the way” shows the worst drop from a high point over the dates you picked, so you can see what you would have had to sit through.
Worked example
Say you had invested $10,000 in the S&P 500 in June 2006 and added $200 every month until June 2026. You’d have put in $58,000.
- It would have been worth about $311,453, a gain of $253,453, with every dividend reinvested.
- Without the dividends it would have been worth $238,589, so reinvesting them added $72,864.
- With dividends reinvested, the index grew about 11.4% a year over the period (9.3% on its price alone).
- Along the way it fell 49% from its peak (October 2007 to March 2009). Anyone who kept investing through that drop still ended up with the result above.
- The same amounts in the Nasdaq Composite would have ended at $408,545 on price alone, after a biggest fall of 48.5%, against $238,589 for the S&P 500 on the same basis.
S&P 500 and Nasdaq returns over 5, 10, 20 and 30 years
How much each index grew a year, on average, over periods ending in June 2026, and what $10,000 invested at the start would have become. “With dividends” is what an investor who reinvested every dividend got; “price only” leaves dividends out.
| Period | S&P 500 with dividends | S&P 500 price only | Nasdaq Composite (price only) |
|---|---|---|---|
| 5 yearsfrom June 2021 | 13.5% a year$18,851 | 11.9% a year$17,577 | 13.1% a year$18,497 |
| 10 yearsfrom June 2016 | 15.5% a year$42,101 | 13.6% a year$35,751 | 18.3% a year$53,694 |
| 20 yearsfrom June 2006 | 11.4% a year$86,272 | 9.3% a year$59,449 | 13.3% a year$121,993 |
| 30 yearsfrom June 1996 | 10.3% a year$189,093 | 8.4% a year$111,444 | 10.8% a year$216,374 |
The figures are for the index itself. A fund that tracks it charges a fee, so a real investor would have ended slightly lower, and taxes aren’t included. Change the dates in the calculator to see any other period.
What $100 or $500 a month in the S&P 500 would have grown to
Investing the same amount every month, with dividends reinvested, for periods ending in June 2026. Each cell shows what the investment was worth and, below it, how much went in.
| Each month | For 10 years | For 20 years | For 30 years |
|---|---|---|---|
| $100 | $27,332$12,000 put in | $112,591$24,000 put in | $243,238$36,000 put in |
| $500 | $136,661$60,000 put in | $562,954$120,000 put in | $1,216,190$180,000 put in |
Monthly investing smooths out the timing: some months buy after a fall, some at a high. The longer the period, the larger the share of the final amount that came from growth rather than from what went in, but no period guarantees a gain, and the next 30 years won’t repeat the last.
S&P 500 and Nasdaq returns by year
How much each index changed in every calendar year from 1972 to 2025, next to inflation that year. Each figure runs from December to December on monthly averages, so it can differ a little from returns quoted to the last trading day. The calculator above can replay any period.
| Year | S&P 500 with dividends | S&P 500 price only | Nasdaq (price only) | Inflation (CPI) |
|---|---|---|---|---|
| 2025 | 15.4% | 14% | 18.5% | 2.7% |
| 2024 | 30% | 28.3% | 34.3% | 2.9% |
| 2023 | 21.7% | 19.7% | 35.5% | 3.4% |
| 2022 | -15% | -16.3% | -30% | 6.5% |
| 2021 | 28.3% | 26.5% | 22.6% | 7% |
| 2020 | 18.5% | 16.3% | 43.7% | 1.4% |
| 2019 | 26.2% | 23.7% | 28.8% | 2.3% |
| 2018 | -1.8% | -3.6% | -1.1% | 1.9% |
| 2017 | 20.9% | 18.6% | 27.3% | 2.1% |
| 2016 | 11.7% | 9.4% | 7.4% | 2.1% |
| 2015 | 2% | 0% | 6.5% | 0.7% |
| 2014 | 15.9% | 13.6% | 16.1% | 0.8% |
| 2013 | 29.7% | 27.1% | 35.7% | 1.5% |
| 2012 | 16.8% | 14.4% | 15.5% | 1.7% |
| 2011 | 2.1% | 0.1% | -1.1% | 3% |
| 2010 | 14% | 11.8% | 18.5% | 1.5% |
| 2009 | 30% | 26.5% | 45.5% | 2.7% |
| 2008 | -39.2% | -40.7% | -42.7% | 0.1% |
| 2007 | 6.3% | 4.4% | 9.4% | 4.1% |
| 2006 | 14.3% | 12.2% | 8.3% | 2.5% |
Show 1972 to 2005
| Year | S&P 500 with dividends | S&P 500 price only | Nasdaq (price only) | Inflation (CPI) |
|---|---|---|---|---|
| 2005 | 7.1% | 5.2% | 4.5% | 3.4% |
| 2004 | 12.8% | 11% | 10% | 3.3% |
| 2003 | 22.3% | 20.2% | 40.9% | 1.9% |
| 2002 | -20.2% | -21.5% | -29.9% | 2.4% |
| 2001 | -12.8% | -14% | -25.6% | 1.6% |
| 2000 | -5.8% | -6.8% | -28.9% | 3.4% |
| 1999 | 21.6% | 20.1% | 80.6% | 2.7% |
| 1998 | 25.5% | 23.7% | 32.2% | 1.6% |
| 1997 | 31.8% | 29.5% | 21.3% | 1.7% |
| 1996 | 23.6% | 20.9% | 23.4% | 3.3% |
| 1995 | 38.4% | 35% | 42.5% | 2.5% |
| 1994 | 0.5% | -2.3% | -3.7% | 2.7% |
| 1993 | 10% | 7% | 15.4% | 2.7% |
| 1992 | 15.5% | 12.1% | 21.5% | 2.9% |
| 1991 | 22.1% | 18.2% | 47% | 3.1% |
| 1990 | -2.4% | -5.7% | -17.5% | 6.1% |
| 1989 | 30.2% | 26.1% | 19.5% | 4.6% |
| 1988 | 18.8% | 14.7% | 19.5% | 4.4% |
| 1987 | -0.1% | -3.1% | -11.4% | 4.4% |
| 1986 | 24.1% | 19.9% | 10.8% | 1.1% |
| 1985 | 31.4% | 26% | 32.4% | 3.8% |
| 1984 | 4.7% | 0.1% | -13.2% | 3.9% |
| 1983 | 23.2% | 17.9% | 19.6% | 3.8% |
| 1982 | 19.2% | 12.6% | 18.2% | 3.8% |
| 1981 | -2.5% | -7.3% | -0.6% | 8.9% |
| 1980 | 30.2% | 23.8% | 33.4% | 12.5% |
| 1979 | 18.2% | 12.2% | 26.9% | 13.3% |
| 1978 | 7.8% | 2.4% | 13.1% | 9% |
| 1977 | -6.3% | -10.4% | 9.7% | 6.7% |
| 1976 | 22.5% | 18% | 24.6% | 4.9% |
| 1975 | 38% | 32.2% | 28.3% | 6.9% |
| 1974 | -26.1% | -29.2% | -34.8% | 12.3% |
| 1973 | -16.9% | -19.3% | -31.9% | 8.7% |
| 1972 | 21.9% | 18.5% | 21.4% | 3.4% |
Even the S&P 500 with dividends fell in 12 of these 54 years, and some falls were steep. Over long stretches the good years have outweighed the bad ones, but there’s no guarantee they will again.
What history can and can’t tell you
Looking back shows how markets have behaved: long periods of growth, interrupted by sharp falls that often took years to recover from. It can’t tell you what happens next. The coming years could be better or worse than any period in the data.
Three things change the real result. Dividends add to it, but only if you reinvest them: switch them off for the S&P 500 to see how much of the result they account for. Fees subtract from it every year, which is why low-cost funds matter. And your behaviour matters most: selling after a crash turns a temporary fall into a permanent loss, while people who kept investing through the drops got the results shown here.