Find Your Coast FIRE Number
Your Coast number is the amount you need invested right now so compound growth does the rest — no more contributions required. Calculate it in seconds.
Your Details
Keep building — you're on your way!
Once you hit your Coast number, compound growth does the rest.
Your Coast FIRE Number
£70,247
Needed today to retire at 65
Gap to Coast
£45,247
Still to save
Retirement Nest Egg
£266,915
At age 65 with 7% return
Retirement Income
£30,000
At 4% withdrawal rate
Your Timeline
Today — Age 30
Current savings: £25,000
Hit Coast Number — Age 42
In 12 years · £70,247 invested
Coasting Period
23 years of compound growth — no contributions needed
Retirement — Age 65
£266,915 nest egg · £30,000/yr income
Portfolio Projection
Assumes 7% nominal annual return. Inflation not adjusted.
What is Coast FIRE and how do I calculate my number?
Coast FIRE is a milestone within the Financial Independence, Retire Early (FIRE) movement. Instead of saving aggressively until you can retire immediately, you save hard untilyour portfolio is large enough that compound growth alone will grow it to your retirement target — then you stop contributing and "coast."
The Coast FIRE number is calculated using the present-value formula: Coast Number = Retirement Target ÷ (1 + r)ⁿ, where r is your expected annual return and n is the number of years until retirement. The retirement target itself comes from the 4% rule — divide your desired annual income by 0.04 (or your chosen withdrawal rate).
Coast FIRE vs regular FIRE — what's the difference?
Coast FIRE
Save until compound growth can reach your target on its own. Then stop contributing — work just to cover expenses. You're coasting to retirement.
Traditional FIRE
Save aggressively until your portfolio can cover all living expenses via withdrawals. Stop working entirely — full financial independence.
The 4% rule explained
The 4% rule (the Bengen rule) states that you can safely withdraw 4% of your portfolio annually in retirement without running out of money over a 30-year period. So if you need £30,000/year, you need a £750,000 portfolio. This forms the foundation of all FIRE planning — and is the default withdrawal rate used in this calculator.
Frequently asked questions
What is the Coast FIRE number?
Your Coast FIRE number is the lump sum you need invested today so that compound growth alone will grow it to your full retirement target — without any further contributions. Once you hit this number, you only need to earn enough to cover your living expenses, not save for retirement.
How is the Coast FIRE number calculated?
Coast FIRE number = Retirement target ÷ (1 + annual return)^years to retirement. The retirement target is typically your desired annual income divided by your withdrawal rate (e.g. 4%). For example, if you want £30,000/year in retirement and use the 4% rule, your retirement target is £750,000. If you have 30 years to retirement at 7% real return, your Coast number is £750,000 ÷ (1.07)^30 ≈ £98,600.
What is the 4% rule and is it relevant in the UK?
The 4% rule (the Bengen rule) states you can withdraw 4% of your portfolio per year in retirement for 30+ years without running out of money, based on US historical data. In the UK, a slightly more conservative 3.5%–4% is generally considered appropriate. The rule is a useful planning heuristic but not a guarantee — your actual safe withdrawal rate depends on investment returns, inflation, and your retirement length.
What is the difference between Coast FIRE, Barista FIRE, Lean FIRE, and Fat FIRE?
Coast FIRE means you have enough invested that compound growth will reach your retirement target without further contributions — you still work to cover expenses. Barista FIRE means you are semi-retired, working part-time in a low-stress job to cover living costs while your portfolio grows. Lean FIRE means full financial independence on a minimal budget, typically under £20,000/year. Fat FIRE means full financial independence with a generous lifestyle, typically £50,000+/year.
How can I reach Coast FIRE faster?
The three main levers are: (1) Save and invest more aggressively in your early years — time in the market matters enormously due to compound growth; (2) Increase your portfolio return by holding low-cost global index funds; (3) Reduce your retirement spending target so you need a smaller pot. Starting early is the most powerful factor — reaching Coast FIRE at 35 instead of 45 dramatically reduces the required Coast number.
Does the Coast FIRE calculator work for UK pension and ISA accounts?
Yes. Your total invested assets include ISA balances, SIPP/pension balances (using the projected transfer value), and any other investment accounts. You can include pension contributions separately — remember that employer contributions and tax relief effectively boost your pension pot. For SIPPs, use the current fund value rather than the contributions you have made.