Investment calculator
Investment calculator for monthly contributions
Enter a starting amount, a monthly contribution, the years and an expected annual return. You see the final balance, what you paid in and how much came from growth.
Increase in the monthly amount and inflation
Converts the result into today's purchasing power.
Portfolio value at the end of each year
- paid in
- return
What the calculation uses
This is a calculator with your assumptions, not a forecast and not a recommendation. The return is assumed to be the same every year; taxes and fees are not deducted.
How it is calculated
- The starting amount is invested on day one. Each monthly contribution is added at the end of the month.
- The balance grows every month at the rate that adds up to your annual return over twelve months.
- If you raise contributions each year, the new amount applies from the first month of the next year.
- With inflation, the final balance is also shown in today's dollars.
Assumptions and notes
- The result is before taxes and fees. How much tax you pay depends on the account: a taxable brokerage account, a 401(k) or an IRA.
- The return is an assumption, not a promise. Real markets move up and down from year to year.
Example: $500 a month for 30 years
You start with $10,000 and add $500 at the end of every month for 30 years, at 7% a year.
You pay in $190,000 in total.
At the end the balance is $660,849, so $470,849 came from growth.
Frequently asked questions
How much will $500 a month be worth in 30 years?
With $10,000 to start and 7% a year, about $660,849 before taxes. You pay in $190,000, and $470,849 comes from growth.
What rate of return should I use?
Many people plan with 6 to 8% a year for a portfolio mostly in stocks. The S&P 500 has averaged about 10% a year since 1926 before inflation, with heavy losses in some years. A lower rate leaves you a margin of safety.
Does the calculator include taxes?
No. In a 401(k) or a traditional IRA you usually pay tax when you withdraw. Qualified withdrawals from a Roth IRA are tax-free. In a taxable account you pay tax on dividends each year and on gains when you sell.