The structure of a retirement projection
A retirement projection has two components and one horizon. The balance you already hold compounds for the whole period. The contributions you will make form an annuity that compounds for progressively shorter periods. Add them and you have the projected balance.
What distinguishes it from a generic future value calculation is length. Thirty or forty years is long enough that the growth term dominates the contribution term, that inflation halves the purchasing power of the result, and that a one-point error in the rate assumption changes the answer by a quarter.
A worked projection
Take a 35-year-old with $60,000 saved, contributing $800 a month, retiring at 65, assuming a 6.5% effective annual return. The existing balance grows to $396,862. The contributions — $288,000 over 30 years — grow to $853,621. The projected balance is $1,250,483.
Read that split carefully. Total money paid in, including the opening balance, is $348,000. The remaining $902,483 is growth. On a thirty-year horizon, roughly 72% of the ending balance was never deposited by anyone.
| Component | Paid in | Value at 65 | Growth |
|---|---|---|---|
| Opening balance $60,000 | $60,000 | $396,862 | $336,862 |
| $800 a month for 30 years | $288,000 | $853,621 | $565,621 |
| Total | $348,000 | $1,250,483 | $902,483 |
The number that actually matters
At 2.5% inflation, that $1,250,483 has the purchasing power of about $596,159 in today's money. Nothing has gone wrong — both figures describe the same portfolio — but only the second one can be compared against a lifestyle you understand.
This is why a retirement target expressed as a round nominal sum is unreliable. A million dollars in 2056 is not a million dollars in the sense the phrase carries today, and a plan built against the nominal figure quietly aims low.
| Age | Nominal balance | Real balance (2.5% inflation) |
|---|---|---|
| 45 | $245,990 | $192,167 |
| 55 | $595,119 | $363,184 |
| 65 | $1,250,483 | $596,159 |
Turning a balance into an income
A balance is not a goal; an income is. The usual conversion applies a withdrawal rate — commonly 4% as a starting reference — to the balance at retirement. At 4%, $1,250,483 supports about $50,019 a year in the first year of retirement, in the dollars of that year.
Working in the other direction is more useful for planning. If you want $60,000 a year in today's money and expect $24,000 from other sources, the gap is $36,000 today, which at 2.5% inflation is $75,512 in thirty years' time. At a 4% withdrawal rate that requires a balance of $1,887,811 — well above the projection, which tells you the plan is short before you retire rather than after.
Target balance = (desired income − other income) × (1 + i)^n ÷ withdrawal rate- Income figures in today's money, inflated to the retirement date
- i — assumed inflation; n — years to retirement
- The withdrawal rate is an assumption, not a guarantee
Closing a gap while the horizon is long
In the example above the shortfall is $637,328 in future dollars. Spread across 360 remaining monthly contributions at a 6.5% effective annual return, closing it requires $597.29 a month on top of the existing $800 — the gap divided by the annuity factor of 1,067.03.
That figure is uncomfortable, and it gets worse with delay. The same gap addressed ten years later has only 240 months to work with, and the annuity factor falls to 479.63, pushing the required top-up to $1,328.80 a month. Ten years of delay does not raise the cost by a third; it more than doubles it. The cost of postponing is not linear, which is the single most important property of the whole calculation.
What the projection does not claim
A projection is not a forecast. It assumes a constant rate, uninterrupted contributions, no job changes, no early withdrawals and no sequence-of-returns effects. Real portfolios violate every one of these.
Its value lies in comparison, not prediction: it tells you whether raising a contribution, delaying retirement by two years or lowering a target moves the plan materially. Those relative answers are robust even when the absolute number is not.
Which levers actually move the number
Four things change a retirement projection: how much you contribute, how long you contribute for, the return you earn, and when you stop. Only two of them are reliably under your control, and one of those two is far more powerful than people expect.
Delaying retirement by two years does three things at once: it adds two years of contributions, gives the whole balance two more years of compounding, and removes two years the balance would have had to fund. That is why a small change to the retirement date often does more than a large change to the contribution.
Raising the assumed return, by contrast, does not change anything in the world. It changes the projection, which is a different thing entirely — and it is the only lever that makes the plan look better while making it more fragile.
Why the projection is most optimistic at the end
A constant-return projection is at its least realistic exactly where it matters most: the years around and after retirement. During accumulation, the order in which returns arrive does not affect the ending balance — a good year followed by a bad one leaves the same result as the reverse.
Once withdrawals begin, order matters enormously. Selling into a falling market removes capital that cannot participate in the recovery, so two retirees with identical average returns can end up in very different positions depending purely on which decade was poor.
This is not a reason to distrust the projection. It is a reason to read the balance at retirement as a starting point for a second question — how long does this actually last under a spending plan — rather than as the end of the analysis.
Educational tool. This article explains arithmetic, not personal circumstances. It is general educational content, not investment, tax or insurance advice, and every figure in it is a projection from stated assumptions rather than a prediction. Check any result against your own situation, and see the editorial policy for how this content is produced and corrected.