FIRE & Retirement Savings Calculator

Why every figure here is in today's dollars

This is the mistake that separates a useful retirement projection from a flattering one, and it is extremely common. Suppose you enter a seven percent expected return and forty-five thousand dollars of annual spending. The forty-five thousand is a number you know from your own life today. The seven percent is a nominal return, and nominal returns contain inflation. If a calculator grows your portfolio at seven percent and then compares the result against twenty-five times today's forty-five thousand, it is racing an inflated portfolio against a finish line that never moved. Over twenty-five years at three percent inflation, that finish line is understated by roughly half, and the retirement age it reports is years too early.

There are two consistent ways to fix it. You can inflate the spending target every year and keep the nominal return, or you can strip inflation out of the return and leave the spending in today's dollars. This calculator does the second, and says so in the result. The real return is computed exactly, as one plus the nominal return divided by one plus inflation, minus one — not as the subtraction shortcut, which drifts once either number is large. Every dollar figure you see is therefore in today's purchasing power, which is the only unit you can actually reason about. A million dollars in 2050 is an abstraction; a million dollars of today's spending power is a life you can picture.

One consequence follows directly and you should know it. Because the model works in real terms, holding your monthly contribution constant means holding it constant in real terms — the projection assumes you raise what you invest each year roughly in line with inflation, as you would if you saved a steady percentage of a salary that keeps pace. If you set up a fixed transfer today and never touch it again, you are contributing a shrinking real amount every year, and you will land short of what this page projects.

Your savings rate moves the answer more than your return assumption

People spend a great deal of energy arguing about whether to assume seven percent or eight, and almost none deciding what fraction of their income they will actually save. The second question dominates, and it is worth understanding why rather than taking it on faith.

Your savings rate does two things at once, in opposite directions, and they compound. Saving a larger share of your income puts more money into the portfolio, which is obvious. But it also means you live on less, and since your target is twenty-five times what you live on, saving more lowers the finish line at the same time as it speeds you toward it. A return assumption only affects the first of those. Move your assumed return by a percentage point and the timeline shifts by a couple of years. Move your savings rate from ten percent to thirty and you change the answer by decades, because you are both accelerating and moving the target closer.

This is also the more honest place to focus, because it is the part you control. You cannot choose what the market returns over the next twenty years. You can choose what your fixed costs are — housing above all, then transport, then the recurring commitments that quietly ratchet up as income does. A person who holds their spending steady while their income grows converts every raise directly into savings rate, and that single habit does more for their retirement date than any plausible improvement in their investment selection. Try it in the inputs above: change the return by one point, then change the monthly contribution by a third, and watch which one moves the age.

Lean, regular and fat FIRE are the same arithmetic with different spending

The labels you see in these discussions describe where someone set the spending input, nothing more. Lean FIRE means a deliberately small annual budget, which produces a small target and an early date, and which leaves very little room between the plan and a bad year. Fat FIRE means a budget with comfort and slack in it, a much larger target, and a later date bought with that margin. Regular or standard FIRE sits between them, usually near what the household already spends.

The reason the distinction matters is not the vocabulary, it is what each choice does to your flexibility. A lean plan is not simply a smaller version of a fat one. If your entire budget is essentials, then a market decline or an unexpected expense cannot be absorbed by spending less, because there is nothing discretionary left to cut. The same portfolio decline that a fat plan absorbs by skipping a holiday can force a lean plan back into the labour market at exactly the moment when doing so is hardest. That asymmetry does not appear anywhere in the twenty-five times multiple, and it is the reason two people with identical numbers can face very different risk.

A useful way to use this page is to run it twice: once at the spending level you would be content with, and once at the spending level you could tolerate for a couple of years if you had to. The gap between those two ages is your real margin of safety, and it is more informative than either number alone.

Sequence-of-returns risk: the average is not the outcome

This calculator applies one steady real return every month. Real markets do not do that, and the difference is not merely cosmetic — it is the single largest gap between this projection and a retirement.

Two portfolios can earn exactly the same average return over thirty years and end in completely different places, depending on when the bad years arrive. While you are still contributing, a crash early on is close to a gift: you are buying at lower prices for years afterwards, and the recovery lifts everything you bought. Once you are withdrawing, the same crash is a serious injury. Selling assets to fund your spending in a year the market fell locks in the loss and permanently removes the shares that would have participated in the recovery. Do that in the first few years of retirement and the portfolio may never catch up, even if the average return over the full period turns out exactly as you assumed.

This is why the years immediately either side of your retirement date carry risk out of all proportion to their length, and why the honest response is not a better return estimate but a plan that does not force selling into a decline. Holding some cash or short bonds to fund the first year or two, keeping some flexibility in the spending, and being willing to delay by a year if the timing is bad are the usual answers. None of them are modelled here. A steady-return projection is a clear way to see how the pieces relate to one another; it is not a forecast, and no calculator that produces a single line can represent this risk.

Why leaving early is harder than the arithmetic suggests

Two large costs sit outside this model, and both fall hardest on people who stop working before the conventional retirement age.

The first is healthcare. For most working people some part of medical cost is bound up with employment, and leaving work can mean arranging and paying for that coverage yourself across the years before any age-based public provision begins. What that costs depends entirely on where you live, what your household looks like and what year it is, and this page has no verified source for any of it, so it will not quote you a figure. What it can tell you is that the gap is real, that it is often large, and that it belongs in the annual spending you enter above rather than being discovered afterwards.

The second is tax. Money in a retirement account is not the same as money you can spend, because withdrawing it may be taxable, and different account types are taxed differently and at different times. Two people with identical balances can have materially different spendable incomes depending on how their savings are distributed across account types and on the rules that apply to them. This calculator models no tax of any kind — not on the growth, not on the withdrawals — so its figures are pre-tax. That is a deliberate limitation rather than an oversight: tax rules vary by jurisdiction and change from year to year, and a page that hard-coded them would go quietly wrong without telling anyone.

The practical way to handle both is to fold your own estimates into the spending input. If you expect to pay for coverage and to owe tax on withdrawals, enter a spending figure that includes them. The target and the age this page reports will move, and they will be closer to the truth for it.