Coast FIRE Calculator with Pension
A pension quietly does years of your portfolio's job. Most coast numbers ignore it completely, so most pension holders are closer than they think.
This calculator splits the target in two: your portfolio covers full spending until the pension starts, then only the gap between spending and pension forever after.
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Coast FIRE with a pension: two targets, not one
A defined-benefit pension changes the coast math structurally, because your portfolio no longer has to fund your whole retirement alone. From the day the pension starts, the portfolio only covers the difference between what you spend and what the pension pays. That perpetual gap, divided by your withdrawal rate, is the first part of the target.
The second part is the bridge. Retire at 60 with a pension that starts at 67 and there are seven years where the portfolio carries everything. The calculator funds those years dollar for dollar on top of the perpetual part, which is a deliberately conservative simplification: bridge money sits close to being spent and should not be counted on to compound.
Run the same numbers in the plain Coast FIRE calculator and you will see the difference a pension makes. With the defaults on this page, the pension cuts the coast number by roughly a third. Couples where one partner has a pension can combine this result with the couples calculator by folding the pension into household spending.
What a pension does to the target
The table holds everything else at this page's defaults: retire at 60, pension starting at 67, $50,000 spending, 4% withdrawal rate, 7% return, coast number computed at age 35.
| Pension per year | Portfolio needed at 60 | Coast number at 35 |
|---|---|---|
| $0 | $1,250,000 | $230,311 |
| $10,000 | $1,070,000 | $197,147 |
| $20,000 | $890,000 | $163,982 |
| $30,000 | $710,000 | $130,817 |
| $40,000 | $530,000 | $97,652 |
What this calculator assumes (and what it leaves out)
The pension is treated as a fixed annual amount from its start age onward, fully reliable, for life. Real pensions can lack inflation adjustment, carry funding risk, or offer lump-sum alternatives; the FAQ covers the honest workarounds. Taxes, fees, survivor benefits, and Social Security are not modeled. If you also expect Social Security, the Social Security version handles claiming ages properly.
Sources: William Bengen's 1994 study in the Journal of Financial Planning and the 1998 Trinity Study. Last reviewed: July 25, 2026, formulas verified against the site's shared coast math.
Frequently asked questions
How does a pension change the Coast FIRE math?
Two ways. From the day the pension starts, your portfolio only has to cover the gap between spending and the pension, which shrinks the perpetual target from spending divided by your withdrawal rate to that gap divided by the rate. And for the years between retiring and the pension starting, the calculator sets aside a bridge fund that covers the missing pension income dollar for dollar.
My pension is not inflation-adjusted. Does the calculator handle that?
Not automatically, and pretending otherwise would be dishonest. A fixed nominal pension buys less every year. The practical adjustment: enter a haircut version of your pension, for example 70 to 80 percent of the promised amount if it starts decades from now, or run the calculator with a real return of about 5% and discount the pension yourself. The result is a planning range, not one exact number.
What if my pension is bigger than my spending?
Then the perpetual part of the target drops to zero and the portfolio only needs to fund the bridge years before the pension starts. The calculator clamps the math this way automatically, and the bridge is capped at your actual spending: the portfolio never needs to replace more pension than you spend.
I get a lump sum choice instead of monthly payments. Which do I enter?
If you plan to take the annuity, enter the annual amount here. If you plan to take the lump sum, add it to your current investments instead and use the regular Coast FIRE calculator: a lump sum is just portfolio money. Comparing the two options properly is a bigger question than this tool answers, and worth doing carefully before you choose.
Who runs this site?
One person, Jonas. The pension variant exists because the plain coast number quietly assumes your portfolio does all the work forever, which is wrong for anyone with a defined-benefit pension, and search data showed people asking for exactly this. Free, no login, and what you type never leaves your browser. A $27 ebook and a $67 workbook fund the site. Not a financial advisor; the about page has more.
Expecting Social Security instead?
The Social Security version handles claiming age: 62, 67 or 70 changes both the benefit and the bridge.
Open the Social Security version →