Free UK tool · Financial Independence, Retire Early
Enter your monthly spend, savings, and contributions to see your FIRE number and freedom date. FIRE — Financial Independence, Retire Early — is the point where your investments can fund your life without you needing to work. Free, private, no sign up.
Your data never leaves your device. Ever.How to use
The FIRE calculator UK above runs the maths the moment you start typing. Here's how to get a useful number out of it.
Below the headline figures you'll see Lean / Your / Fat FIRE milestones (50%, 100%, 150% of your annual spend) and a "What if…" strip — toggle them to see how saving £200 more, reducing your retirement spend, or investing a raise changes your timeline.
Understanding FIRE
FIRE is built on a handful of ideas that, once they click, change how you think about money for good.
The 4% rule comes from the Trinity Study, which back-tested decades of US stock and bond returns to find the highest withdrawal rate a portfolio could sustain for 30+ years without running out. The headline number — 4% per year, adjusted for inflation — is the basis of the modern FIRE movement. Your FIRE number is simply your annual spending divided by your safe withdrawal rate (SWR). At a 4% SWR, that's the same as 25× annual spending.
The original 4% rule assumed a 30-year retirement. If you're retiring in your 30s or 40s with a 50+ year horizon, a more cautious 3% to 3.5% SWR is widely recommended. It also handles "sequence-of-returns risk" better — the danger of retiring just before a major market downturn. The Cautious option in the calculator above uses 3.5%.
Lean FIRE is the minimalist version. You retire on a smaller portfolio (often under £500k in the UK) by keeping spending tight — modest housing, no expensive holidays, careful with cars and eating out. The trade-off is freedom from work in exchange for a deliberately frugal lifestyle. The calculator's Lean FIRE milestone is set at 50% of your stated annual spend.
Fat FIRE is the opposite — retire with enough that comfort, travel, and the occasional luxury are baked in. It's typically £1.5M+ in the UK and means working longer or earning more along the way. The calculator's Fat FIRE milestone is set at 150% of your stated annual spend.
Barista FIRE is a hybrid. You save enough that part-time work covers your day-to-day spending while your portfolio compounds untouched until traditional retirement age. Often paired with a job that provides health benefits, social structure, or a sense of purpose without a full-time salary load. It's a popular middle path for people who don't want to never work again — they just don't want their job to be load-bearing.
£750,000 sounds enormous. But the FIRE number is meant to last decades. The reason the maths works is compounding: at a 7% real return, money roughly doubles every decade. £100k saved at 30 is around £400k by 50 without adding a single pound — and most people are still contributing the whole way. The single biggest lever isn't your income — it's your savings rate. At 50% you reach FI in ~17 years from zero. At 25%, ~32 years.
UK specifics
UK FIRE planning leans heavily on tax wrappers. Stocks and Shares ISAs let you invest up to £20,000 a year with tax-free growth and tax-free withdrawals at any age — making them the cornerstone of an early-retirement bridge before pensions can be accessed. SIPPs (Self-Invested Personal Pensions) bolt on income tax relief at your marginal rate — a higher-rate taxpayer effectively gets a 40% boost on every contribution — but the money is locked away until 57 (rising to 58 in 2028). Most UK FIRE plans use both: ISAs for the early-retirement bridge, SIPP for the years from 57 onwards.
If you're under 40 and don't already have one, a Lifetime ISA gives you a 25% government bonus on contributions up to £4,000 a year. Withdraw before 60 (other than for a first home) and you lose the bonus plus a small penalty, so it's a long-horizon vehicle. Useful FIRE tool, but it's a commitment.
The full new State Pension is around £11,500 a year (2025/26) and currently starts at age 67, rising to 68 in the 2040s. If you're aiming for traditional retirement age, factor it in. If you're aiming to retire in your 30s or 40s, leave it out as a buffer — bridge to State Pension age on your own portfolio, treat anything from age 67 onwards as upside not load-bearing.
The growth rate cards in the calculator (4% to 11%) are nominal — i.e. before inflation. The 4% rule is already inflation-adjusted because it includes annual increases, so your FIRE number is in today's pounds. If you assume 7% nominal growth and 2.5% inflation, your real return is roughly 4.5%. Most FIRE planning is done in real terms because it makes future spending power easier to reason about.
If your employer matches pension contributions, contribute at least up to the match. It's an instant 100% return, on top of tax relief. For a basic-rate taxpayer with a 5% match, every £1 of your take-home pay turns into roughly £2.50 inside the pension. Hard to beat as a FIRE strategy.
FAQ
The questions people most often type into Google about UK FIRE and retiring early.
The standard rule of thumb is 25× your annual spending, based on a 4% safe withdrawal rate. If you spend £30,000 a year, your FIRE number is £750,000. If you spend £40,000, it's £1 million.
That figure represents the size of an investment portfolio that should sustainably fund your lifestyle indefinitely. Use the FIRE calculator above to see your exact number based on your monthly spending.
The 4% rule says that if you withdraw no more than 4% of your initial portfolio each year (adjusted for inflation), your money should last at least 30 years. It comes from the Trinity Study, which back-tested decades of stock and bond market data.
The 4% figure is the most common safe withdrawal rate, though many in the UK FIRE community prefer a more cautious 3–3.5% to account for sequence-of-returns risk and longer horizons. The calculator above lets you switch between Cautious (3.5%), Balanced (4%), and Flexible (5%).
Two calculations sit underneath. Your FIRE number = annual spending ÷ safe withdrawal rate. Your freedom date is then the number of months it takes for your current savings, plus monthly contributions, to compound up to that target at your chosen growth rate.
Growth rate (4% cash to 11% aggressive equity) and withdrawal approach are independent — change either to see how it affects your timeline.
Three levers: spend less, earn more, invest the difference in low-cost diversified funds. The savings rate matters more than the absolute income. At a 50% savings rate, financial independence is roughly 17 years away regardless of income. At 25%, it's about 32 years.
UK-specific tools that help: max out your ISA allowance (£20,000 a year, tax-free growth and withdrawals), use a workplace pension or SIPP for higher-rate tax relief, and consider a Lifetime ISA if you're under 40.
Yes, but it requires either a high savings rate or a high income — usually both. To retire at 40 starting from zero at 25, you'd need to save roughly 50–60% of your take-home pay every year and invest it in growth assets.
Use the calculator above to model it: enter your current age, monthly spend, and contributions to see if 40 is realistic for you. Be aware that pension savings can't usually be accessed until 57 (rising to 58 in 2028), so most early retirees use a "bridge" of ISAs and taxable accounts to cover the gap.
Lean FIRE means retiring on essentials only — typically a smaller portfolio (often under £500k in the UK) with a frugal lifestyle.
Fat FIRE means a comfortable retirement with travel, eating out, and buffer — usually £1.5M+ portfolios.
Barista FIRE is a hybrid: you save enough that part-time work covers your day-to-day spending while your portfolio compounds untouched, often via a job that provides health benefits or social structure rather than a full salary.
It depends on your age and how conservative you want to be. The full new State Pension is around £11,500 a year and starts at age 67 (rising to 68).
If you're aiming for traditional retirement age, factoring it in is reasonable. If you're aiming to retire in your 30s or 40s, leave it out as a buffer — you'll bridge the gap to State Pension age on your own portfolio, and anything from age 67 onwards is upside, not load-bearing.
Yes, completely free. There's no sign up, no email collection, no paywall. Everything runs in your browser — none of the figures you enter are sent to a server or stored anywhere outside your device.
The full picture
Vault is the home for everything this calculator hints at — your net worth, your spending, your plan, your tax — all in one private view. Same principles: free, private, local only. Nothing you enter ever leaves your device.
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