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✦ Free UK calculator · 2025/26 rules

Coast FIRE Calculator UK

Coast FIRE is the moment your investment pot is big enough that, even if you stop contributing today, compound growth alone gets you to a full retirement number by your target retirement age. This calculator does the maths in real (inflation-adjusted) terms — and flags the UK pension access cliff that most generic FIRE calculators ignore.

🏖️
Your Coast FIRE numbers
All figures in today's £. Updates as you type.
years
years
£
£
%
%
£
Your full FIRE number
£875,000
Spending ÷ withdrawal rate (today's £)
Your Coast FIRE number
£250,000
What you need today to coast
Pot at retirement (no more contribs)
£308,000
Today's pot, compounded
If you keep contributing
£800,000
At your current rate
Coast FIRE progress 32%
⏳ Not yet — but you're on track.
Your portfolio needs to reach £250,000 to hit Coast FIRE. At your current rate, you'd get there in around 8 years — roughly age 40.
ⓘ All figures in today's pounds — this calculator works in real (after-inflation) terms. Coast FIRE assumes you stop contributing entirely; "If you keep contributing" continues at your current monthly rate to the target age. UK State Pension assumes the full new flat-rate amount (~£11,500/yr 2025/26) starting at age 67. This is a planning aid, not personal financial advice.
✦ The full picture

What is Coast FIRE, and why is it the most useful FIRE milestone?

Most people think of FIRE as a single moment — the day your portfolio is large enough to live off forever. But there's a much earlier, more reachable milestone that almost every UK investor will hit before full FIRE: Coast FIRE. It's the point where you've front-loaded enough money into your portfolio that you no longer need to add anything — compound growth on its own carries you to a full FIRE number by your target retirement age. Your job income only has to cover your living costs from now until retirement. The retirement saving is done.

It matters because it's a permission slip. Hit Coast FIRE in your 30s and you can switch to a lower-paid job you actually like, drop to four days a week, take a sabbatical, start a business — all without ever touching your existing pot, and still arrive at full retirement on schedule. That's a fundamentally different kind of freedom from waiting decades for full FIRE.

The formula

Coast FIRE is built from three numbers: your full FIRE number, your real return assumption, and the years until you retire.

The Coast FIRE formula
Coast FIRE Number = FIRE Number ÷ (1 + r)n
where r = real annual return · n = years until retirement

And the FIRE number itself is just:

FIRE Number
FIRE Number = Annual spending ÷ Safe withdrawal rate
e.g. £35,000 ÷ 4% = £875,000

So if you want £35,000/year in retirement and your full FIRE number is £875,000, and you're 32 with a target retirement age of 60 at 5% real return, your Coast FIRE number is £875,000 ÷ (1.05)28 ≈ £224,000. Hit £224,000 today and you can stop contributing, and the pot will grow to £875,000 by age 60. That's the entire game.

Coast FIRE is in real terms — read this carefully

The single biggest mistake in DIY Coast FIRE calculators is mixing real and nominal numbers. A 7% nominal return at 3% inflation is only a 4% real return — so if you use a 7% return alongside today's spending number, you'll dramatically understate the pot you need, because you've forgotten that future spending will be inflated too.

The fix is to work in real terms throughout: real return, real spending, real pot. The calculator above does this — when it says you need £224,000, that's £224,000 in today's purchasing power. Whatever the nominal pound figure ends up being in 2050, it'll buy you the same as £224,000 buys today.

The UK pension access cliff

Coast FIRE works the same way mathematically in any country, but UK investors have a wrinkle US calculators ignore: SIPPs and workplace pensions are locked until age 57 (rising to 58 from April 2028, with longer-term plans to track 10 years before state pension age).

This matters if your target retirement age is below 57. Say you want to retire at 50 with a £35,000/year lifestyle. Your full FIRE number is still ~£875,000 — but if all £875,000 is inside a SIPP, you can't touch any of it for seven years. You need a bridge fund in ISAs or other accessible accounts to cover from 50 to 57. That's typically £35,000 × 7 ≈ £245,000 in ISAs minimum.

The split, in practice, looks like:

📊 What WealthR does differently

The full WealthR app models the bridge fund explicitly — it runs separate projections for your accessible (ISA, GIA) pot and your locked (SIPP, pension) pot, then tells you at what age each runs out and whether the SIPP unlocks before the ISA depletes. It's the gap most calculators miss.

What withdrawal rate to use in the UK

The famous 4% rule (the Trinity Study) was built on US data — mostly US large-cap equities and US Treasury bonds, over 1926–1995. It's a useful starting point but probably optimistic for a UK investor in 2025 because:

The current consensus among UK FIRE planners is somewhere in the 3.25%–3.5% range for high confidence. 3.5% is a reasonable default — it gives you a pot 14% larger than the 4% rule, but with a meaningful margin against bad luck.

Should you actually stop contributing once you hit Coast FIRE?

Mathematically, yes — that's the definition. In practice, almost no-one does. The reasons:

A common compromise: at Coast FIRE, drop to just enough to capture employer match and use your dividend allowance, and redirect everything else to whatever lifestyle change you wanted Coast FIRE to enable.

How to actually get to Coast FIRE faster

✦ How the calculator works

Methodology

1
Calculate your FIRE number
FIRE Number = annual retirement spending ÷ safe withdrawal rate. Lower SWR = larger pot. If State Pension is included, we deduct it from spending after age 67.
2
Calculate years to retirement
n = target retirement age − current age. Used as the compounding horizon for Coast FIRE.
3
Compute Coast FIRE number
Coast FIRE = FIRE Number ÷ (1 + r)n. The pot you need today such that, with no more contributions, compound growth at rate r reaches the FIRE number by retirement.
4
Project your current pot forward
Pot at retirement (no more contributions) = current pot × (1 + r)n. Compared against the FIRE number to show whether you've already hit Coast FIRE.
5
Project with continued contributions
FV = current_pot × (1 + r)n + monthly × 12 × [((1 + r)n − 1) ÷ r]. Standard future value of a growing series, applied annually.
6
Find Coast FIRE date
If you haven't hit Coast FIRE yet, we solve year-by-year for when (current_pot + contributions) compounded forward equals the Coast FIRE number for that year.
7
Render in real terms
All values shown in today's pounds. The growth rate is the real (after-inflation) return, so the FIRE number doesn't drift over time.
✦ Common questions

Coast FIRE UK FAQ

What is Coast FIRE?
Coast FIRE (Financial Independence, Retire Early) is the point at which your existing investment pot is large enough that, if you stopped contributing today, compound growth alone would carry it to a full retirement number by your target retirement age. You still need to cover your living costs in the meantime, but you no longer need to save for retirement.
How is Coast FIRE different from regular FIRE?
Regular FIRE (Lean, Fat, or Standard) means you have enough invested to live entirely off withdrawals today. Coast FIRE is the earlier, lower bar — you have enough that compound growth will get you to a full FIRE number by retirement age without further contributions. It's a milestone on the way to FIRE, not a replacement for it.
What is the formula for Coast FIRE?
Coast FIRE Number = FIRE Number ÷ (1 + r)n. Where FIRE Number = annual spending ÷ safe withdrawal rate (typically 4%), r is your real annual return (after inflation), and n is the number of years between today and your target retirement age. The calculator above does the maths for you including UK tax-wrapper considerations.
Does Coast FIRE work in the UK?
Yes — the maths is universal, but UK investors need to think carefully about wrapper access. SIPPs and workplace pensions are locked until age 57 (rising to 58 from April 2028, planned to track 10 years before state pension age). If you want to retire before that, you need enough in ISAs, taxable accounts or property to bridge the gap. WealthR models this UK-specific "pension access cliff" explicitly.
What withdrawal rate should UK investors use?
The 4% rule (Trinity Study) was based on US data with mostly US equities. UK investors typically use 3.25% to 3.5% for higher confidence over a 30+ year retirement, given lower long-term UK returns and currency exposure. A common compromise is 3.5%, which gives a slightly higher FIRE number than 4% but more margin for sequence-of-returns risk.
What real return should I use for UK?
A "real" return is the return after inflation. For a globally diversified equity portfolio, 4–5% real is a common assumption (5% if you're more optimistic, 4% if conservative). For a 60/40 stock-bond portfolio, 3–4% real is more realistic. Avoid using nominal returns of 7–8% in a Coast FIRE calculation — they'll badly understate the pot you need because they ignore that future spending will be inflated too.
Should I include the UK State Pension?
It depends. The full new State Pension is around £11,500/year for 2025/26 and starts at age 66 (rising to 67 from 2028). You can subtract it from your retirement spending need before calculating your FIRE number — but only if you'll have 35 qualifying years of National Insurance contributions and you trust it to still exist in roughly that form. Many UK FIRE planners model it as a "bonus" rather than a guaranteed input.
What about ISAs vs SIPPs for Coast FIRE?
ISAs are accessible at any age (penalty-free, tax-free), so they're the natural bridge for early retirees. SIPPs and pensions get tax relief on contributions (worth 20–45% depending on your band) but are locked until 57+. A common UK FIRE strategy is to fill the ISA first if retiring before 57, then prioritise SIPP for the long-haul retirement years where the higher-rate tax relief and tax-free growth compound over 30+ years.
I've hit Coast FIRE — can I really stop saving?
Mathematically yes, but in practice most people who hit Coast FIRE keep contributing at least something. The reasons: it gives you margin against poor returns, it lets you retire earlier than your target age, it covers unforeseen costs, and the habit is harder to restart than to maintain. A common move is to keep contributing enough to capture employer pension match plus your ISA dividend allowance, and stop everything else.
Does WealthR calculate my Coast FIRE number automatically?
Yes. The full WealthR app pulls your tracked ISA, SIPP, pension and other investments together, applies your chosen real return and withdrawal rate, and projects your Coast FIRE date alongside your full FIRE date — including the UK pension access cliff and a separate "bridge fund" calculation if you want to retire before 57.

Want this baked into your full plan?

WealthR's full app projects your Coast FIRE date alongside your full FIRE date, models the UK pension access cliff, and runs a separate "bridge fund" calculation if you want to retire before 57. It pulls from the ISAs, SIPPs and pensions you already track. Free to try, takes about five minutes.

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