FIRE Number Calculator

What’s your FIRE number?

Pick your region, enter your expenses, get the size your portfolio needs to reach so you no longer need a paycheque, plus years to FI at your current pace and a Coast FI checkpoint. Same math fjordFIRE runs in-app.

How the FIRE number works

The classic FIRE rule: your portfolio reaches financial independence when it’s big enough that withdrawing a small percentage each year (the safe withdrawal rate, or SWR) covers your annual expenses indefinitely. The number itself is just annual expenses ÷ SWR: at 4% SWR, that’s 25× annual expenses; at 3.5%, ~28.5×; at 3%, ~33×.

The Trinity Study’s 4% rule was derived from US markets, so it isn’t gospel everywhere. But inventing a different withdrawal rate for every country would be false precision, and there’s no honest data for it. So fjordFIRE ships one transparent, well-sourced baseline: a 4% safe withdrawal rate on a 5% real return. Only inflation is set from where you live. You can override any of it if your own history suggests something different.

How years-to-FI is calculated

Closed-form future-value math, the same formula the in-app FI projection uses:

n = ln((FI + C/r) / (P + C/r)) / ln(1 + r)
where P = current portfolio, C = annual savings,
r = REAL (inflation-adjusted) return, FI = target

Two important details. First, r is the real return, not nominal. The calculator converts via the Fisher equation: real = (1 + nominal) / (1 + inflation) − 1. This is why a 12% nominal return in India with 6% inflation behaves nothing like a 12% nominal return in Norway with 3% inflation. Second, this assumes flat monthly savings; the in-app version supports rising contributions (salary growth above inflation) with a growing-annuity formula.

Coast FI explained

Coast FI is the moment your portfolio is large enough that, even if you stopped saving today, it would compound to your full FI number by your target retirement age. It’s a softer milestone than full FI: it means you can switch to part-time work, take a sabbatical, or just stop optimising savings and still land where you want. The math: coastNumber = FI / (1 + r)^(coastAge − currentAge), using the real return rate.

What this calculator deliberately does not do

It assumes one currency, flat monthly contributions, and a fixed real return, none of which are how most lives actually work. It treats all your invested assets as one bucket; in reality, locked retirement accounts (401k, PPF, pension) behave differently from liquid investments because you can’t withdraw from them at any age. It doesn’t model taxes, fees, sequence-of-returns risk, or the fact that markets don’t deliver their average return every year.

The in-app version of this addresses each of those: multi-currency portfolios, separate Protect / Growth / Retire / Move pillars, Monte Carlo with 1,000 simulated futures, contribution-growth modelling, and a What-If sandbox where you can drag the savings rate or expected return and watch the FI date move in real time.

What the full version adds

• Coast FI, Lean FI, Fat FI, and Barista FI: all four variants on one screen.
• Monte Carlo: 1,000 simulated futures showing the probability fan around your projected FI date.
• What-If sandbox: drag savings rate, return, or expenses, watch the FI date shift instantly.
• Per-member FI in two-person households: the math respects joint ownership and per-member expense shares.
• Multi-currency: every account converted live, FX vs organic savings decomposed.
• Recalculated every month from your actual check-in numbers, not a one-shot snapshot.

Go deeper: Read: The 4% Rule → · Coast / Barista / Lean / Fat FI → · Everything on FIRE →

Try the companion calculator: How long would your money last abroad? →

How we think about the numbers behind every figure: The method →

Run this again next year and the answer will have moved. fjordFIRE updates the projection at every check-in.