FIRE Number (25× expenses)
£625,000
Enter your annual spending and savings rate to estimate your FIRE target and timeline. This estimator intentionally starts simple and shows practical outputs you can refine over time.
£625,000
17.0 years
-
£25,000
£50,000
£550,000
£337,500
This is a planning estimate, not financial advice. Use it as a baseline, then stress test with lower returns and higher inflation assumptions.
FIRE stands for Financial Independence, Retire Early. In practical terms, it means building a portfolio that can fund your living costs before traditional retirement age. In the UK, this goal is shaped by tax wrappers, pension rules, and the timing gap between the age you want to stop working and the age you can draw pension funds. Most people planning early retirement in Britain use a mix of workplace pension, SIPP, and Stocks and Shares ISA, because each account solves a different time horizon problem. Your pension is powerful for long-term tax efficiency, while your ISA is usually the key bridge for years before pension access.
The starting calculation is simple by design: estimate annual spending in retirement and multiply by 25. That gives a rough target pot under a 4% withdrawal assumption. For example, if your annual spending is £25,000, a typical base target is £625,000. This is not a guaranteed safe number in all market conditions, but it is still one of the most useful frameworks for planning because it forces clarity. You stop asking vague questions like “How much is enough?” and start asking practical ones: “What can I save?”, “How many years does this imply?”, and “What changes most improve the timeline?”
A strong FIRE plan is not only about compounding; it is about system design. You need an investment strategy, an account structure, a withdrawal strategy, and a risk plan for rough years. Many UK households discover that once these pieces are visible in one place, decisions become easier: raise savings rate, reduce fixed costs, avoid tax drag, and build flexibility before market downturns happen. The calculator above is meant to support exactly that process.
The headline formula is: FIRE number = annual expenses × 25. It is equivalent to saying that if you withdraw around 4% of your portfolio each year, your money may last over a long retirement horizon under historical assumptions. The key word is “may.” The 4% guideline comes from back-tested scenarios and is a framework, not a promise. Real life includes inflation spikes, tax changes, major spending shocks, and market cycles that can look very different from the long-term average.
Even so, the formula is useful because it creates a clean first benchmark. If your target lifestyle costs £30,000 per year, the base FIRE number becomes £750,000. If your true spending is £20,000, your baseline falls to £500,000. This is why accurate expense tracking matters so much more than optimistic return assumptions. Overestimating expected returns by 1% can lead to disappointment; underestimating annual spending by £5,000 can break a drawdown plan.
Use the formula as a floor for planning, then layer prudence: model slightly higher spending, include maintenance and one-off costs, and test lower withdrawal rates like 3.5% for extra robustness. Many UK FIRE planners run two numbers: a core target at 25× and a conservative target at 28× to 30×. The bigger point is not to find a mathematically perfect number on day one, but to build a target that survives bad years without panic selling.
Your savings rate is often the strongest driver of how quickly you reach financial independence. Income matters, but the percentage of income you keep and invest has direct influence on both your future portfolio and your current spending baseline. If two people earn the same salary and one saves 20% while the other saves 50%, their timelines to FIRE can differ by decades. That is why many early retirees focus first on recurring costs, housing efficiency, transport choices, and avoidance of lifestyle inflation.
The table below gives a useful set of reference points used in this calculator. It includes the required examples for UK FIRE planning discussions and helps you sanity-check outputs before you make assumptions about your own timeline.
| Savings Rate | Estimated Years to FIRE | What it often means in real life |
|---|---|---|
| 10% | 43 years | Slow path; high dependence on long career duration. |
| 20% | 32 years | Better than average but still heavily tied to full-time work. |
| 30% | 24 years | Meaningful acceleration, especially with pension match and tax efficiency. |
| 40% | 20 years | Solid FI trajectory if investment costs are low and consistent. |
| 50% | 17 years | Strong acceleration; one of the classic FIRE thresholds. |
| 60% | 12 years | Very fast path that usually needs deliberate lifestyle design. |
| 70% | 8.5 years | Extremely aggressive, often with high income or temporary sprint phase. |
These timelines are estimates, not guarantees. They assume consistency, market participation, and controlled spending over long periods. Life introduces career changes, children, caring responsibilities, housing moves, and health costs. The right approach is to use a savings-rate model as directional guidance and review yearly rather than obsess over monthly volatility. If your savings rate rises by 5 to 10 percentage points and stays there, the long-term effect is often larger than short-term return noise.
For most people in the UK, the normal minimum pension access age is moving to 57 from 2028. This matters because many FIRE plans fail at the transition point, not because the total wealth target is impossible, but because money is trapped in the wrong account at the wrong time. You can be “wealthy on paper” with pension assets and still run into cashflow stress before pension access if you do not build a bridge.
Think in phases. Phase one is from your FIRE date to age 57. Phase two is from age 57 to your state pension age. Phase three begins when state pension starts around age 66-67 for many people. Each phase can use a different withdrawal mix. Early phase withdrawals usually rely more on ISA or taxable accounts. Middle phase can include pension drawdown with ISA support. Later phase may need smaller portfolio withdrawals if state pension covers part of your spending.
In practice, this means your account location is part of your FIRE strategy, not admin detail. If your target is to retire at 45, you need roughly 12 years of accessible capital before pension access. If your target is 52, you need around 5 years. The calculator shows an ISA bridge estimate based on your expenses and age so you can quickly see whether your liquid-access plan is proportionate to your timeline.
An ISA bridge is simply the pot you draw from before pension access. For UK FIRE planning, this is often the difference between a smooth transition and a stressful one. You build the bridge by directing part of your long-term investments into a Stocks and Shares ISA or other accessible accounts while still contributing to pension for tax relief and long-term compounding. The split between pension and ISA depends on target retirement age, employer match, tax band, and how much flexibility you want in your 40s and early 50s.
A useful planning method is to ring-fence “bridge years” first. If you expect £28,000 annual spending and plan to stop work at 48, you may need around nine years before pension access at 57. That suggests a bridge requirement in the region of £252,000 before accounting for growth, partial earnings, or market risk buffers. Many people then add one to two years of cash or short-duration assets to reduce forced selling in downturns. This approach can look conservative, but it improves sleep and decision quality when markets drop.
ISA bridge planning also supports flexibility around part-time work, freelancing, or mini-retirements. You do not need a rigid binary of “full-time job” versus “zero earnings forever.” A practical UK plan might combine modest earned income, ISA withdrawals, and gradually increasing pension use after age 57. The objective is sustainability and freedom, not a perfect spreadsheet. The phrase “ISA bridge to pension age” is not jargon for specialists only; it is one of the most practical concepts for any UK household targeting early retirement.
Sequence of returns risk is one of the biggest hidden threats to early retirement plans. It describes the danger of poor market returns in the first years after you stop working. If losses happen early while you are withdrawing, portfolio damage can compound because you are selling units at depressed prices and leaving fewer assets to recover later. Two portfolios can have the same average return over 30 years but very different outcomes if the order of returns differs.
You can reduce sequence risk without abandoning growth entirely. Common methods include maintaining a cash buffer for one to three years of spending, reducing discretionary withdrawals during bear markets, and keeping an asset allocation that you can hold through volatility. Flexible spending rules work well: withdraw less in bad years, more in strong years, and avoid anchoring to a fixed inflation-adjusted withdrawal regardless of market conditions. Some early retirees also keep optional income streams like consulting, tutoring, or seasonal work to lower pressure on the portfolio when markets are weak.
The practical message is simple: your withdrawal process matters as much as your FIRE number. A portfolio target reached with no withdrawal plan can still fail under stress. A slightly smaller target with strong flexibility and risk controls may prove more durable. That is why this page treats the 25× number as a starting point, then adds pension staging, bridge planning, and resilience tactics. Sequence risk is not a reason to give up on FIRE; it is a reason to plan withdrawals with discipline before you need them.
Lean FIRE, Fat FIRE, and Barista FIRE describe different lifestyle and risk preferences rather than different maths. Lean FIRE means retiring on a comparatively low budget and usually requires high cost control. It can work well for people with low fixed costs, location flexibility, and simple spending priorities. The trade-off is that there is less margin if inflation or health expenses rise faster than expected. Lean FIRE often benefits from a bigger emergency buffer and a willingness to earn occasional income.
Fat FIRE targets a higher spending level with greater comfort, travel, and discretionary margin. It needs a larger portfolio and often a longer accumulation phase, but it can provide resilience in uncertain economic periods. In UK terms, Fat FIRE planners may prioritise larger ISA balances, lower withdrawal rates, and stronger protection against tax and inflation drift. This approach can reduce stress in retirement, but reaching the number may take longer and require sustained high earnings or very high savings discipline.
Barista FIRE sits between full retirement and full employment. You use invested assets to cover part of your spending while part-time income covers the rest. The “barista” label is symbolic: any lower-stress paid work can fit. This model is popular because it lowers required portfolio size, cuts sequence risk, and preserves social structure. For many UK households, Barista FIRE is the most realistic path: it reduces pressure on both the bridge period and long-term withdrawal assumptions without forcing an all-or-nothing career decision.
The right model is personal. Some people start with Lean FIRE as an escape plan, move to Barista FIRE for flexibility, and later transition toward Fat FIRE if investments and income outperform. Others prefer a direct Fat FIRE target and accept a longer runway. The common thread is deliberate design: define your minimum acceptable lifestyle, preferred lifestyle, and resilient lifestyle. If those three numbers are clear, your financial decisions become far easier and less emotional.
The UK state pension is not usually enough for a high-spending retirement on its own, but it can materially lower required portfolio withdrawals in later life. Many FIRE plans improve when modelled in two phases: before state pension and after state pension. If your desired annual spending is £30,000 and state pension contributes £11,500 to £12,000 per year in today’s terms, your portfolio only needs to cover around £18,000 to £18,500 after state pension starts, rather than the full £30,000.
That is why the calculator displays a “later-life target after state pension.” It is not a replacement for your full FIRE number, because you still need sufficient assets for years before state pension age. But it helps explain why a staged drawdown plan can be more efficient than one static number. For people retiring very early, this distinction is especially useful: your bridge and mid-life portfolio may carry heavier withdrawal demand, then pressure can ease once state pension begins at around age 66-67.
Make sure your assumptions are realistic. State pension age and entitlement rules can change, so build margin rather than treating current values as fixed forever. Check contribution records periodically and include a conservative buffer in your model. The goal is not to depend entirely on policy stability; it is to use likely state support as one component of a diversified plan that remains robust if conditions shift.
A technically sound FIRE plan in Britain usually combines the following foundations. First, capture employer pension match because it is effectively immediate return on contribution. Second, use tax wrappers efficiently: pensions for relief and long-horizon growth, ISAs for flexibility and pre-pension access. Third, keep investment costs low through broad, diversified funds and avoid frequent strategy changes driven by headlines. Fourth, revisit your plan annually with updated spending and allocation rules rather than daily reaction to market movement.
Tax efficiency can be as important as raw return. Two portfolios with similar market performance can produce very different retirement outcomes if one uses wrappers well and the other leaks to tax unnecessarily. For higher-rate taxpayers, pension relief can significantly boost effective savings power; for early access needs, ISA liquidity is critical. The most resilient UK FIRE setups respect both truths at the same time instead of choosing one wrapper exclusively.
Discipline often beats complexity. Many successful FIRE journeys are built on ordinary habits repeated for a long time: automated monthly investing, rising savings with pay growth, controlled fixed costs, and consistent rebalancing. If you prefer detailed forecasting, keep it useful by using ranges rather than single-point certainty. Model optimistic, base, and conservative cases. If all three cases still support your intended retirement window, your plan is likely robust enough for real life.
The UK FIRE community has grown into a valuable source of practical experience, especially around tax wrappers, withdrawal strategy, frugal systems, and mindset during downturns. Community spaces can help normalise long-term investing behaviours that feel unusual in mainstream spending culture. Seeing real examples of people tracking expenses, discussing portfolio allocations, and iterating retirement plans over years can make the process less abstract and more achievable.
Use community input carefully: learn principles, not copy-paste decisions. Your housing costs, family setup, health profile, and career optionality are unique. The best use of community is to test your assumptions, find blind spots, and gather practical tools. Then apply what fits your life and ignore what does not. FIRE succeeds when your plan is personally sustainable, not when it looks perfect on social media.
Accountability is one of the biggest behavioural benefits. A simple annual review post or personal checkpoint can keep your strategy on track when motivation dips. Over long periods, behavioural consistency usually drives outcomes more than tactical optimisation.
Run a structured review once per year. Update annual spending in today’s pounds. Recalculate your 25× baseline and a conservative alternative. Check whether your savings rate improved, stayed flat, or drifted down. Verify that your ISA bridge still covers the years before pension access. Review contribution splits between pension and ISA based on your target retirement age and tax position. Confirm your emergency and cash buffers are still adequate. Rebalance investments if your allocation has drifted meaningfully.
Then test your withdrawal resilience with a sequence-risk mindset: what would you do if markets fell 30% in your first two years after FIRE? If your plan has no answer, improve it now. Add flexibility rules, optional income routes, and staged spending priorities. Keep your essentials funded first, discretionary spending second, and large one-off purchases conditional on portfolio health. This makes your plan adaptive rather than brittle.
Finally, review life design, not just numbers. FIRE is a financial tool for time autonomy, not a finish line in itself. Define what your weeks look like after full-time work, what relationships and routines matter, and where part-time income could add meaning rather than stress. The most successful plans combine robust maths with a realistic post-work lifestyle.
Your FIRE number is the invested portfolio needed to support your spending without depending on full-time employment. In UK planning, a common baseline is annual expenses multiplied by 25, linked to a 4% withdrawal guideline. If spending is £25,000 per year, the baseline number is £625,000. This is a planning anchor rather than a guaranteed safe outcome. People usually refine it with lower withdrawal assumptions, staged spending, and policy-aware assumptions for pension and state pension.
It is useful, but not universal. The 4% rate comes from historical modelling and can break under difficult return sequences, high inflation periods, or rigid spending behaviour. UK FIRE planners often improve durability with flexible withdrawals, global diversification, and one to three years of safer assets or cash to avoid forced selling in market stress. Treat 4% as a starting framework. If your plan still works at 3.5% in conservative scenarios, resilience usually improves meaningfully.
Because your retirement date and pension access date are not always the same. If you retire before age 57, pension money may be inaccessible for years. Without a bridge, you may need to return to work or sell assets in poor market conditions. A UK FIRE plan should explicitly map account access by age. Pension can be excellent for long-term tax efficiency, but ISAs and accessible investments are usually the bridge for pre-57 years.
Most successful UK FIRE plans use both. Pension is often the most tax-efficient long-term vehicle, especially with employer contributions and higher-rate tax relief. ISA provides flexible withdrawals before pension age and simplifies early-retirement cashflow. The right split depends on your target retirement age, earnings, tax band, and flexibility preference. If you plan to retire far before 57, ISA allocation typically needs to be meaningful to support bridge years.
State pension can lower later-life portfolio withdrawals, so many people plan in stages. Before state pension starts, your portfolio may cover most spending. After state pension starts, required drawdown often falls. This does not remove the need for a strong early-retirement pot, but it can lower pressure in later years and improve sustainability. The key is not to over-rely on policy assumptions: build buffers and review entitlement records regularly.
Sequence risk means poor returns early in retirement can damage long-term outcomes more than identical poor returns later. You are withdrawing while the portfolio is down, which can permanently reduce compounding capacity. Common defences include flexible spending rules, temporary income, a cash reserve, and avoiding panic allocation changes. Managing sequence risk is one reason why withdrawal strategy is as important as hitting the target FIRE number.
Lean FIRE aims for early retirement on a lower annual budget. Fat FIRE targets higher spending and more discretionary comfort, requiring a larger portfolio. Barista FIRE combines part-time income with investment withdrawals, reducing portfolio pressure and increasing flexibility. None is universally better. The best fit depends on your cost base, risk tolerance, and desired lifestyle. Many people move between these categories over time as priorities and circumstances evolve.