FIRE calculator
Financial independence means a pot big enough that a safe withdrawal rate covers your spending for good. Enter what retired-you would spend and what you're saving now, and see your FIRE number, the age you reach it, and the question UK savers must answer that American FIRE blogs never mention: what pays the bills before your pensions open at 57.
You and your saving
How the number is built
What saving more into ISAs does
What FIRE means, in one formula
FIRE number = annual spending ÷ withdrawal rate. That's the whole engine. Spend £30,000 a year and trust a 4% withdrawal rate, and you need £750,000, which is the same thing as 25 times your spending. Prefer a more careful 3.5% and the multiple becomes roughly 28.6 times, or £857,143. Notice what the formula doesn't contain: your salary. FIRE runs on the gap between what you earn and what you spend, which is why cutting £1,000 a year of permanent spending does double work, shrinking the target by £28,600 at the same moment it frees money to save.
The bridge problem UK savers have and American blogs don't
Most UK retirement money lives in pensions, and pensions have a legal opening age: 55 today, rising to 57 in April 2028, which is the figure this calculator uses. Retire at 48 and there can be nine years in which your pension pot is enormous, growing, and useless for buying groceries. The years in between must be funded from ISAs, general accounts and cash. This calculator checks that bridge properly: it prices the years from your FIRE age to 57 and tests them against your accessible savings alone, which is a test plenty of impressive-looking plans fail. The fix is usually not saving more overall but changing where the saving goes, tilting monthly money toward ISAs even though pensions carry better tax relief. And from 67 the State Pension arrives, £12,548 a year in 2026/27 terms with a full record, quietly covering a big slice of most people's spending for the rest of the plan.
Lean, Fat, Barista and Coast
The subtypes are variations on this page's formula, and each now has a dedicated tool. Lean FIRE runs it on stripped-back spending, around £20,000 a year or less, with a budget builder that prices every £100 a month in pot and in working years. Fat FIRE runs it on £60,000 or more, where the simple formula genuinely breaks: drawdown at that scale pays income tax, so the true pot is bigger than the untaxed division suggests. Barista FIRE mixes a part-time wage with a smaller pot, and its calculator tests the whole two-phase journey rather than just the smaller number; the quick version lives in the Barista field above. And Coast FIRE asks when saving becomes optional rather than when work does. The one-tap presets above set the Lean and Fat spending levels if you want the quick look without leaving this page.
Why the default rate is 3.5%, not 4%
The famous 4% comes from research on 30-year retirements using American market history. Retire at 45 and you're planning for 50 years, in a portfolio that will live through several crashes, with UK costs and UK taxes. A withdrawal rate is really a claim about surviving the worst sequence of returns you might meet, and the longer the horizon, the more worst cases exist: the volatility drag calculator shows the mechanism that makes order matter. Most careful UK planning uses 3% to 3.5% for early retirement, and the slider lets you test how much the choice moves the target, which is a lot. For the fuller simulation, with the State Pension, access ages and year-by-year drawdown, run your numbers through the retirement age calculator as well: this page finds the target, that one stress-tests the journey.
Common questions
What is a FIRE number and how is it calculated?
Your FIRE number is annual retirement spending divided by a safe withdrawal rate — the pot at which investment income can replace your salary indefinitely. At the classic 4% rate that means 25 times annual spending (£30,000 a year needs £750,000); at the more cautious 3.5% many UK planners prefer, roughly 28.6 times (£857,143).
What are Lean FIRE, Fat FIRE and Barista FIRE?
The same formula run on different lifestyles. Lean FIRE targets stripped-back spending of roughly £20,000 a year or less, giving a smaller pot you can reach sooner. Fat FIRE funds £60,000+ and needs £1.5m or more. Barista FIRE mixes a part-time wage with a smaller pot — the income covers part of the bills, so the investments only fund the shortfall. Coast FIRE is different again: enough invested that growth alone finishes the job while you keep working.
Can I use my pension if I retire early in the UK?
Not before the normal minimum pension age: 55 now, rising to 57 on 6 April 2028 for most schemes. Retire younger than that and the years until your pension opens must be funded from ISAs, general investment accounts and cash — the "bridge" this calculator checks. The State Pension arrives later still, at 67, but then covers a meaningful slice of most people’s spending for life.
Is the 4% rule safe for early retirement?
It was derived from 30-year retirements using US market history, so a 45-year-old planning 50 years of drawdown is outside its evidence base. Long horizons meet more bad sequences of returns, UK returns and costs differ, and most careful UK planning uses 3–3.5% instead. The difference is material: at £30,000 of spending, moving from 4% to 3.5% raises the target from £750,000 to £857,143.
These results are estimates for general information only and are not financial advice. Investment returns are not guaranteed and withdrawal-rate research is based on the past — check your plan with a qualified adviser. Read the full disclaimer.