Monthly Investment Calculator

Enter the monthly amount, the return you expect, the number of years and, if you plan to raise the amount every year, the increase percentage. The table shows the amount invested and the projected value at the end of each year.

How to use the monthly investment calculator

1. Monthly investment: the amount you plan to put in each month, such as an automatic transfer to a brokerage account, an IRA or a 529 plan.
2. Expected return: the average yearly return you want to test. The default is 8%. Try several values rather than relying on one.
3. Investment period: how many years you plan to keep contributing, up to 40.
4. Yearly step-up: the percentage by which you raise the monthly amount each year. Leave it at 0% for a flat amount. Set it to 3% to keep pace with typical raises or inflation.

The result shows the estimated value at the end, the total you put in and the estimated gains. The year-by-year table shows the monthly amount in each year, the total invested so far, the projected value and the gains.

How the projection is calculated

The calculator adds your contribution at the start of each month and then grows the balance by one month of return, using the annual rate divided by 12. It repeats that for every month in the period. If you set a step-up, the monthly amount rises by that percentage at the start of each new year.

With the defaults, $1,000 a month at 8% for 10 years:

• Total invested: $120,000
• Estimated value: about $184,166
• Estimated gains: about $64,166

Early contributions have the most time to grow. The first $1,000 grows for 120 months, the last one for one month. That is why the gains column grows slowly at first and faster later on.

Why time matters more than the amount

The same $1,000 a month at 8%, over different periods:

Years	Invested	Estimated value	Gains
10	$120,000	$184,166	$64,166
20	$240,000	$592,947	$352,947
30	$360,000	$1,500,295	$1,140,295

Doubling the time from 10 to 20 years more than triples the value, and at 30 years gains make up three quarters of the balance. Compare someone who invests $2,000 a month for 20 years with someone who invests $1,000 a month for 30 years. Both put in a similar amount, $480,000 versus $360,000, but the 30-year investor ends with about $1.5 million against about $1.19 million. Starting early is the strongest lever you have.

Choosing a return rate

The return is the input that matters most and the one you control least. Some points to keep in mind:

• US stocks have returned roughly 10% a year on average over long periods, before inflation, but with large swings. Some decades were far below that.
• A mix of stocks and bonds has historically returned less than all stocks, with smaller drops.
• Fees reduce your return directly. An expense ratio of 0.05% on an index fund costs almost nothing; 1% a year in fund and advisory fees can take a large share of the gains over 30 years.
• Inflation reduces what the money will buy. To see the result in today’s dollars, enter the return minus an inflation assumption, for example 8% minus 3%, so 5%.

Run the calculator at 6%, 8% and 10% to see a range. On $1,000 a month for 10 years, that range runs from about $164,699 to about $206,552. The high case has almost twice the gains of the low case, from the same deposits. Plan around the lower figures.

What a yearly step-up does

Raising the contribution each year makes a large difference because it adds money while you still have years left to grow it. With a 10% yearly step-up, $1,000 a month at 8% for 10 years grows to about $275,792, compared with $184,166 without the step-up. You invest $191,249 instead of $120,000, so part of the difference is simply more money in. The rest is growth on the extra contributions.

A step-up that matches your raises is easy to keep up, because your take-home pay does not fall. Many 401(k) plans offer automatic yearly increases of 1% of pay. Use the step-up field to see what that would add.

Reading the year-by-year table

The table is useful for setting milestones. With $1,000 a month at 8%, the projected value passes $100,000 in year 7 and the yearly gains overtake the yearly contributions in year 10. Comparing the table with your real statements each year shows whether you are ahead of or behind the plan. If you are behind after a bad year in the market, that does not mean the plan has failed. It means the order of returns has been unkind so far. If you are behind because contributions were skipped, the table shows how much to add to catch up.

You can also use the table backward. If you need $250,000 in 15 years for a goal, try monthly amounts until the final row reaches that figure at a return you are comfortable with.

Where monthly investing fits

The calculator suits any regular contribution into an investment account:

• A 401(k) or 403(b) through payroll. Enter your contribution plus any employer match as the monthly amount.
• A traditional or Roth IRA. The IRS sets an annual limit; divide it by 12 to fund it evenly.
• A taxable brokerage account with automatic investing into index funds or ETFs.
• A 529 college savings plan, with the period set to the years until college.

For a fixed yearly contribution, such as funding an IRA in one deposit each January, the retirement savings calculator models that pattern more closely. If you want a guaranteed return for money you will need sooner, compare the savings plan calculator for monthly deposits or the CD calculator for a lump sum.

Taxes and the result

The projection is before tax. What you keep depends on the account:

• In a traditional 401(k) or IRA, growth is tax-deferred and withdrawals are taxed as income.
• In a Roth account, qualified withdrawals are tax-free.
• In a taxable account, dividends are taxed each year and gains are taxed when you sell, at long-term capital gains rates if you held the investment more than a year.

Limits of any projection

Real returns come in an uneven order. Two investors with the same average return can end with very different balances depending on when the good and bad years fall, especially near the end. A steady monthly contribution helps, because you buy more shares when prices are low, a pattern known as dollar-cost averaging. But it does not remove the risk. Treat the result as one scenario among several, and review your plan every year or two with your actual balance.

If a goal is less than five years away, a projection like this is less useful, because a single bad year can take a large bite out of the balance with little time to recover. For short goals, guaranteed savings usually fit better.

Nothing you enter is sent anywhere. The projection runs in your browser.

Learn more

How monthly investment returns are calculated explains the formula and why your brokerage statement’s return differs from it. Increasing your contributions each year shows what a yearly raise does to the final balance.

Frequently asked questions

How much will $500 a month be worth in 20 years?

At an 8% average return, about $296,000, of which $120,000 is what you put in. At 6% it is about $232,000 and at 10% about $383,000. Enter $500, 20 years and each rate to see the year-by-year detail. Returns are not guaranteed, so treat these as scenarios.

What return should I use?

For a diversified stock portfolio over 20 years or more, 6% to 8% is a cautious range for planning. Use less for a mix with bonds or for shorter periods. To see the result in today’s money, subtract around 2% to 3% for inflation. Avoid using a recent good year as your assumption.

Does the calculator include fees?

No. Subtract your total yearly costs from the return. If your funds charge 0.2% and you expect 8% before fees, enter 7.8%. If you pay an adviser 1% of assets on top, enter 6.8%. Over decades, a one-point difference in fees can change the ending balance by a fifth or more.

Is investing monthly better than a lump sum?

If you already have the lump sum, investing it at once has historically come out ahead more often, because markets rise more often than they fall. Monthly investing spreads the risk of a bad entry point and fits how most people earn money. For regular savings from income, monthly investing is the natural choice.

Why is my brokerage return different from the calculator?

Your account’s return depends on the actual order of market moves and the timing of your deposits. The calculator assumes the same return every month. Brokerages often report a time-weighted or money-weighted return, which can differ noticeably from a fixed-rate projection even over the same period.

Should I include my employer match?

Yes. The match goes into the same account and grows the same way. If you contribute $500 a month and your employer adds $250, enter $750. Check whether the match vests over time, because unvested matching money can be lost if you leave the job early.