What this calculator answers
The existing millionaire calculator takes your current monthly savings and tells you when your portfolio reaches the million. This calculator turns the question around. You set a target year and get the monthly savings that fit it mathematically. If your real goal is living off your wealth rather than the round million, the financial independence calculator derives the target amount from your monthly spending. The guide Live off your investments then shows which costs, later income and risks belong in your plan alongside the pure monthly savings.
The defaults are $25,000 starting capital, a target of one million dollars, 30 years and a 7% annual return. This gives required monthly savings of around $692.37. Without starting capital it would be around $855.10. You can replace the million with any other target amount.
The calculation also shows how much you paid in yourself by the target and which part comes from the assumed return. This split in particular prevents a common error in thinking. A target of one million does not mean that you have to set aside a million from your income.
How I calculate the required monthly savings
The monthly savings are paid in at the end of each month. This is called payment in arrears. Your existing capital, on the other hand, earns a return from the first month.
First, I convert the annual return into a monthly return. At 7% a year, that is not simply 7 divided by 12. Because of compounding, this approximation would give 7.23% by the end of the year. I use the geometric conversion. 7% a year becomes around 0.5654% a month, and twelve such months give exactly 7% again.
Then the starting capital grows over the entire term. At 7%, $25,000 becomes $190,306.37 in 30 years, even if not a single further dollar is added. That leaves $809,693.63 missing to reach the million. The annuity formula spreads this missing end value over 360 monthly payments and takes into account that the first payment works for almost 30 years, but the last one for only one month.
The result is $692.37 a month. Over 30 years, including the starting capital, you pay in $274,253.12. The remaining around $725,746.88 comes from the return in the smooth model.
Why time changes the monthly savings so much
With the same $25,000 starting capital and the same return, you need around $1,779.69 a month for a million in 20 years. At 30 years it is around $692.37, at 35 years only around $428.35. So ten additional years lower the amount by far more than a third.
There are two effects behind this. You pay in for longer, and every early payment earns a return for longer. The second effect is often underestimated. The $692.37 you pay in during the first month grows, mathematically, to more than $5,000 over 30 years at a steady 7%. The last payment, by contrast, stays almost unchanged.
The relationship also works the other way round. If you start later, you can only make up for lost time with a considerably higher monthly amount, more starting capital, a smaller target or a higher return assumption. Of these, the return is the only lever you do not control.
Do not rely on 7% alone
A steady return does not exist in a real portfolio. The calculator still needs a number. So treat it as a scenario, not as a forecast.
For $25,000 starting capital, 30 years and a target of one million, the range looks like this:
| Annual return | Required monthly savings |
|---|---|
| 3% | $1,623.12 |
| 5% | $1,093.91 |
| 7% | $692.37 |
| 9% | $392.63 |
Between 5% and 9% lie more than $700 of monthly savings. A plan that only works with the high value is therefore fragile. It is better to calculate a range and check once a year whether your actual portfolio value is still between the scenarios.
The order of the stock market years is also missing from the model. In the accumulation phase, an early price drop can help, because later payments buy more shares. A drop shortly before the target, on the other hand, can push the date back. Two portfolios can reach the same average over 30 years and take completely different paths along the way.
The million is a gross target
The calculator does not deduct any taxes. A portfolio value of one million before a complete sale is not automatically one million of available money after tax. How much goes to taxes depends on the country you live in, on your purchase prices and on the shares you choose to sell. Check the rules where you live, or ask a tax advisor.
Ongoing costs are missing as well. If a TER lowers the expected market return from 7% to 6.8%, the required monthly savings in the default example go up. Further differences from tracking difference, spreads and order costs can come on top. In the ETF savings plan calculator you can check the cost effect separately.
Inflation turns a million into a moving target
A million in 30 years buys less than a million today. At 2% inflation, it then corresponds to around $552,000 in today’s purchasing power. At 3%, around $412,000 remains.
If your target comes from a specific expense, project this expense forward. At 2% inflation, one million in today’s purchasing power corresponds to a nominal target of around $1.81 million in 30 years. You can enter exactly this value above as your target amount.
Another option is to calculate with a real return. If you simply subtract 2% inflation from a 7% return, you are left with roughly 5%. The target amount then stays easier to understand in today’s purchasing power. Mathematically, the exact real return would be slightly lower than the simple difference. For planning, it matters more that you do not deduct inflation both in the target amount and in the return at the same time. Otherwise you count it twice.
What $100 a month really achieves
The question about the million can make smaller goals look needlessly small. At 7%, $100 a month grows to around $247,154 over 40 years. You paid in $48,000. In the model, the rest comes from the return. That is not a million, but it is not a meaningless amount either.
So first set a goal that belongs to your life. That can be a portfolio size for retirement, a sum for the deposit on a home or a safety cushion. The calculator works with $100,000 just as it does with a million. After that you can put the million next to it as a second mark.
How to use the figure in everyday life
Start with the amount that is already genuinely invested today. Money in your checking account that you need for running expenses is not starting capital. Then set a target year and calculate with three returns.
Round the calculated monthly savings up. An amount of $692.37 is easier to automate as $700. The small buffer does not fully absorb costs and individual missed months, but it makes the plan less tight.
Check your position once a year. If your portfolio is above the middle path, you do not have to lower the amount right away. If it is below, you can adjust the time, the monthly savings or the target amount. A higher return cannot be ordered.
If you already have fixed monthly savings and want to know the target date instead, switch to the calculator “When will I be a millionaire?”. Both pages use the same monthly logic. One solves for the time, this one solves for the monthly savings.