How does the calculator solve for time?
Most savings calculators ask how much you will have after a set number of years. This one flips the question. It uses the same future value formula, a starting balance growing at a monthly rate plus a stream of monthly deposits, and solves for the number of months at which the total reaches the target.
The solution uses logarithms. The ratio of (target × monthly rate + deposit) to (starting balance × monthly rate + deposit) tells you how many times the growth factor must be applied. Dividing the log of that ratio by the log of (1 + monthly rate) gives the months, which the calculator rounds up to the first month the target is passed.
Total you contribute is the monthly deposit times that number of months. Interest earned is the target minus your contributions and starting balance.
N = ln((T × i + C) ÷ (S × i + C)) ÷ ln(1 + i) i = annual return ÷ 12
- N
- months to reach the target (rounded up)
- T
- target amount
- S
- current savings (starting balance)
- C
- monthly contribution
- i
- monthly rate
Example: $40,000 saved, $1,200 a month, aiming for $1 million
Scenario: Sam, 35, has $40,000 invested and adds $1,200 a month. Sam assumes an illustrative 7% average annual return, compounded monthly, with deposits at the end of each month.
- Monthly rate7% ÷ 12 = 0.5833% (0.0058333)
- Ratio($1,000,000 × (0.07 ÷ 12) + $1,200) ÷ ($40,000 × (0.07 ÷ 12) + $1,200) = $7,033.33 ÷ $1,433.33 ≈ 4.906977 (from the unrounded amounts)
- Monthsln(4.906977) ÷ ln(1.0058333) = 1.590658 ÷ 0.0058164 = 273.48, rounded up to 274 months
- Time to goal274 months = 22 years and 10 months
- Contributions and growth$1,200 × 274 = $328,800 contributed; $1,000,000 − $40,000 − $328,800 = $631,200 from growth
Sam would cross $1,000,000 in about 22 years and 10 months, at roughly age 58.
Real returns vary year to year and the result is before taxes and in future dollars, so treat the date as a rough guide.
When does a time-to-target calculation help?
Setting a long-range milestone
A date is easier to plan around than an abstract total. Knowing roughly when you might reach a target helps you judge whether your current savings rate fits your plans.
Weighing a raise in contributions
Try adding $200 or $400 a month and compare the dates. The calculator shows how many years each increase shaves off.
Testing other targets
The target does not have to be a million. Enter your own number, such as a figure from a retirement estimate or financial independence plan.
Stress-testing the return
Run the same plan at a lower return. If the date moves out by years, the plan depends heavily on that assumption.
What mistakes skew a time-to-a-million estimate?
Using a cash savings rate for invested money, or the reverse
A savings account and a diversified investment portfolio have very different expected returns and risks. Match the rate to where the money actually sits.
Treating a million as fixed buying power
In 25 years, a million dollars will buy much less than it does today. Raise the target or subtract inflation from the return to plan in today's dollars.
Ignoring taxes
In a taxable account, some growth is taxed along the way, which slows the climb. Tax-advantaged accounts can delay or avoid that, depending on the type.
Assuming the monthly amount never changes
Contributions often rise with income and sometimes pause. Rerun the calculator when your saving changes instead of relying on an old date.
How much do the return and the monthly amount change the date?
Both matter a great deal on a target this large. For Sam, each one-point change in the return moves the date by about one and three-quarter to two and a half years. Raising the monthly amount from $1,200 to $2,000 moves it from about 22 years and 10 months to 18 years.
The return is the input you control least, so many savers plan around a cautious rate and treat any extra growth as a bonus. The monthly amount is the lever you control most.
| Scenario | Months | Time to goal |
|---|---|---|
| $1,200 a month at 5% | 329 | 27 years, 5 months |
| $1,200 a month at 6% | 299 | 24 years, 11 months |
| $1,200 a month at 7% | 274 | 22 years, 10 months |
| $1,200 a month at 8% | 253 | 21 years, 1 month |
| $800 a month at 7% | 320 | 26 years, 8 months |
| $2,000 a month at 7% | 216 | 18 years, 0 months |
Terms used on this page
- Compound Interest
- Compound interest is interest earned or charged on both the original principal and the interest that has already built up. Each period's interest is added to the balance, so the next period's interest is a little larger. Over long stretches, compounding makes savings grow faster and unpaid debts grow faster too.
- Rule of 72
- The Rule of 72 is a mental-math shortcut for estimating how long money takes to double at a fixed compound rate: divide 72 by the annual percentage rate. At 8%, money doubles in about nine years. It works best for rates between roughly 4% and 12% and can also estimate how fast debt or inflation doubles.
- Inflation
- Inflation is the general rise in prices over time, which reduces how much a dollar can buy. In the US it is most often measured by the Consumer Price Index, published monthly by the Bureau of Labor Statistics. When your savings earn less than inflation, their purchasing power shrinks even though the dollar balance grows.
- Net Worth
- Net worth is the value of everything you own minus everything you owe. Assets include cash, savings, investments, retirement accounts, home and vehicles; liabilities include mortgages, car loans, student loans and card balances. It is a snapshot of your overall financial position, and tracking it over time shows whether you are moving forward.
Save a Million Calculator: common questions
How long will it take me to save a million dollars?
It depends on three things: what you have now, what you add each month and the return. Starting from $40,000 and saving $1,200 a month at an illustrative 7%, it takes about 22 years and 10 months. At 5%, it takes about 27 years and 5 months. Enter your own figures above for a personal estimate.
How much do I need to save a month to become a millionaire?
That depends on how many years you have and the return. To find it with this calculator, adjust the monthly contribution until the time to reach the goal matches your deadline. For a target-first answer, the savings goal calculator on this site solves directly for the monthly amount given a goal and a date.
How long to save $1 million investing $1,000 a month?
Starting from zero at an illustrative 7% return compounded monthly, $1,000 a month takes about 27 years and 7 months (331 months) to pass $1 million. With a head start, it takes less. The return is the biggest uncertainty, so try the calculator with a lower rate to see a more cautious timeline.
Why does the last part of the climb go faster?
Because growth is a percentage of the balance. Early on, most of each year's increase comes from your deposits. Near the target, the balance is so large that monthly growth alone can exceed your contribution. In the example, growth supplies $631,200 of the million, most of it in the later years.
Is a million dollars enough to retire on?
It might be, depending on your spending, other income, location and how long retirement lasts. A million spread over 30 years of withdrawals is a very different picture from a million needed to last 40. The savings withdrawal calculator on this site can show how long a balance lasts at a given withdrawal rate.
Does the save a million calculator account for inflation?
No, the target and results are in future dollars. To plan in today's purchasing power, either raise the target by expected inflation or lower the return by an assumed inflation rate. For example, using 4% instead of 7% roughly approximates a 7% return with 3% inflation, and lengthens the timeline accordingly.
How does the rule of 72 relate to saving a million?
The rule of 72 estimates doubling time by dividing 72 by the return. At 7%, money doubles about every 10.3 years. It ignores new deposits but is a handy sanity check: a balance of $250,000 at 7% would become about $500,000 in roughly a decade and $1 million in roughly two, without further saving.
What counts toward the starting balance?
Include money already set aside for this goal, typically retirement and investment accounts you intend to leave invested. Leave out your emergency fund and money earmarked for nearer-term goals, since you plan to spend it. The starting balance compounds for the whole period, so it has an outsized effect on the date.
What is interest earned in the results?
It is the part of the target supplied by growth rather than by you: the target minus your starting balance and all your monthly contributions. In the example, $631,200 of the $1,000,000 comes from growth. It is shown before taxes, so in a taxable account the amount you keep would be somewhat lower.
Sources
- Compound Interest Calculator — U.S. Securities and Exchange Commission (Investor.gov). Accessed October 17, 2026.
- Rule of 72 (glossary) — U.S. Securities and Exchange Commission (Investor.gov). Accessed October 17, 2026.
- Consumer Price Index — U.S. Bureau of Labor Statistics. Accessed October 17, 2026.
We cite primary sources: regulators, central-bank data and federal agencies. Worked examples on this page are our own calculations, last checked October 17, 2026. See our methodology.