Total you contributed
$130,000
Enter a starting balance, a monthly contribution and an assumed annual return. The calculator gives you the future value — and, more usefully, splits it into the part you paid in and the part compounding produced, then finds the year the second overtakes the first.
The annual return is an assumption you supply, not a forecast. This page performs no market prediction and no historical simulation; it applies your chosen rate at monthly compounding so that the arithmetic is transparent and reproducible by hand.
| Years | Projected balance |
|---|---|
| 5 | $49,973 |
| 10 | $106,639 |
| 15 | $186,971 |
| 20 | $300,851 |
| 25 | $462,290 |
| 30 | $691,150 |
| 40 | $1,475,521 |
Two things grow at the same time. The opening balance compounds on itself, and the monthly contributions form a stream of payments that each begin compounding from the month they are made. The two are computed separately and added.
P — the starting balance, compounded for the whole periodM — the monthly contribution, compounded from the month it is paidr — the monthly rate, which is the annual rate divided by twelven — the number of months, which is the years multiplied by twelveContributions are assumed to arrive at the end of each month. Paying them at the start instead adds one extra month of compounding to every contribution, which is a small but real difference and one reason two calculators can disagree by a few percent on an identical set of inputs.
The headline balance is the least informative number this page produces. The split between contributions and growth is where the useful information lives, because it tells you whether you are still in the phase where your own deposits dominate or the phase where the balance is doing the work.
| After | You contributed | Growth added | Growth share of the balance |
|---|---|---|---|
| 5 years | $40,000 | $9,973 | 20.0% |
| 10 years | $70,000 | $36,639 | 34.4% |
| 15 years | $100,000 | $86,971 | 46.5% |
| 20 years | $130,000 | $170,851 | 56.8% |
| 30 years | $190,000 | $501,150 | 72.5% |
| 40 years | $250,000 | $1,225,521 | 83.1% |
$10,000 opening balance, $500 a month, 7% annual return, monthly compounding
On this schedule the crossover happens in year 17, when accumulated growth passes accumulated contributions. Before that point the balance is mostly a record of your own deposits. After it, the balance is mostly a record of time. That is why the last decade of a long plan feels so different from the first: between year 20 and year 30 the balance rises from $300,851 to $691,150, more than it did across the entire first twenty years combined.
There is a practical implication that runs against intuition. Because late growth is large, starting five years earlier is worth far more than contributing more later. Five extra years at the beginning of a 30-year plan adds growth on top of growth for the full term; five extra years at the end adds growth on top of almost nothing. Anyone choosing between starting now at a modest amount and starting later at a larger one should compute both configurations on this page before deciding.
Three limits apply to every projection of this kind, and none of them are fixable by better arithmetic.
The honest use of this tool is as an experiment rather than an answer. Change one input at a time, watch which one moves the result, and find out how sensitive the plan is to each. The retirement savings calculator converts the balance into an income figure if that is the question you are actually asking.
This page will accept any figure, and it deliberately does not supply one. What can be said is that the assumed rate compounds over the whole period, so a one percentage point difference is large: on the default inputs, 6% produces $227,447 less than 7% over 20 years. The safest approach is to run the calculation at a modest rate and again at a pessimistic one, and treat the gap between them as your uncertainty rather than choosing a single number and believing it.
Yes, and monthly is better for the same total paid. Each monthly contribution begins compounding as soon as it is paid, while the same money contributed once a year sits outside the account earning nothing for an average of six months. On the default figures the difference runs to a few thousand dollars over 20 years. It is a modest effect next to the choice of return assumption, but it is free.
Usually one of four things: whether contributions are treated as arriving at the start or the end of the month, whether the compounding frequency is monthly or annual, whether the assumed return is stated in nominal or real terms, and whether fees have been deducted. This page uses end-of-month contributions, monthly compounding, a nominal return and no fees, and every one of those choices is stated so that you can reproduce the number elsewhere.
The arithmetic is exactly how compounding works if the return is constant. What is not realistic is the constant part. A real portfolio does not return 7% every year; it returns a scatter of positive and negative years that averages out over long periods, and the sequence matters. The tool answers the question it is asked — what a constant rate produces — and the caveats section explains where that diverges from a real account.
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Cluster us/investing · Unit us-compound-interest-calculator · Engine compound-growth / fv · Method: Monthly compounding on the opening balance plus an ordinary annuity of monthly contributions, both at the annual rate divided by twelve, evaluated at the end of each month.