July 3, 2026·7 min read

How to calculate your FIRE number (the honest version)

Your FIRE number is annual expenses times 25. That's the easy part, and where most calculators stop. The honest version pins down three inputs nobody agrees on: which expenses, in which currency, funded by which money.

Your FIRE number is your annual expenses multiplied by 25. That is the whole formula, and it is where almost every calculator stops. The multiplication is the easy part. The honest work is in three inputs nobody pins down: which expenses, in which currency, funded by which money. Get those wrong and a confident number is confidently wrong. Here is the full version.

Run it as you read: our free FIRE Number calculator takes your expenses, your withdrawal rate, and your currency, and gives you the number this post is about. No sign-up.

The formula, and the one number inside it that moves

Written out honestly, your FIRE number is:

FIRE number = annual expenses ÷ safe withdrawal rate
At a 4% rate, that’s × 25. At 3.5%, × 28.6. At 3%, × 33.3.

“× 25” is not a law. It is just 1 ÷ 0.04. The multiplier is the inverse of your withdrawal rate, and your withdrawal rate depends on how long your retirement is and how flexible your spending can be. If you’re retiring early, the multiplier climbs. We unpacked why in The 4% rule, for people who don’t retire in America. For the rest of this post, pick your rate and hold it steady.

Which expenses? (not the ones you have today)

Your FIRE number is built on your retirement spending, not your current spending, and the two are rarely the same. The mortgage that finishes, the kids who leave, the commute that vanishes: all subtract. The healthcare that grows, the travel you’re finally free to do: those add. Start from today’s essential expenses, then adjust deliberately for the life you’re actually funding.

For couples, there is a further split: your number is built from your share of household expenses, not the household total. Two people rarely retire on the same day or need the same pile. We covered the couple-specific math in FIRE for couples in different currencies.

Which currency?

Pick the currency you will actually spend in retirement, and keep the whole calculation in it: expenses, withdrawal rate, inflation assumption, all of it. If your spend is NOK and your target is NOK, a FIRE number computed on USD assumptions is quietly wrong. Mixing currencies inside the formula is where the silent errors live.

Worked example. A couple retiring in Oslo. Retirement essential spend: 480,000 NOK a year. Horizon is long, so they use a 3.5% withdrawal rate (× 28.6). Naive FIRE number: 480,000 × 28.6 ≈ 13.7m NOK. That is the number most calculators would hand them, and it is too high, for the reason in the next section.

Subtract the money you don’t have to fund yourself

Your portfolio does not have to cover your entire retirement spend. A state pension and any occupational pension will cover a slice of it. Your portfolio only has to fund the gap. So the honest formula is gap × multiplier, not total spend × multiplier.

Back to the Oslo couple. If folketrygden plus their occupational pensions are projected to cover ~45% of their retirement spend, the portfolio gap is ~264,000 NOK a year. Gap × 28.6 ≈ 7.6m NOK, not 13.7m. Skipping this step inflates your target by a factor that can add a decade of imaginary saving. Estimate your own projection at Min pensjon (or your country’s equivalent) and feed the gap in, rather than guessing.

Separate the money you can’t touch yet

One more split, and it’s the one early retirees miss most. The money locked in pensions until an access age counts toward your Total FI, but it does nothing to shorten the countdown to the day you can actually stop working. The pile that has to carry you from your retirement date to your access age is your Accessible FI, and it’s a smaller, more urgent number. Track both. Retire on the accessible one.

Putting it together

The honest FIRE number, in one line: (your share of retirement essential expenses, in your spend currency, minus the part pensions cover) ÷ your safe withdrawal rate, held as two figures, accessible and total. Every one of those clauses is a place the easy “× 25” version quietly lies to you.

Once you have the number, the next question is how long it takes to reach it. We walk through the levers that set your timeline in How long until you’re financially independent?.

How fjordFIRE handles this

fjordFIRE’s FIRE number is computed from your withdrawal rate, your currency, and your assumptions, with regional defaults to start you sane and full override on every one. It runs per pillar and per member, and it holds Accessible FI and Total FI as separate figures rather than collapsing them into one flattering total.

The one piece we don’t automate: the pension-gap netting. You still estimate your state and occupational projection at Min pensjon and feed the gap into your retirement-expense assumption yourself. The math frame is solid and the currency handling is honest; the country-specific projection is a manual input, and we’d rather tell you that than fake a number we can’t stand behind.

The waitlist is open here. Drop your email. No bank logins, no surveillance.

Go deeper: Lesson: The 4% Rule · Lesson: The FI Spectrum.

Companion tools: FIRE Number calculator · Coast FI calculator.