Coast FIRE Calculator UK: When Can You Stop Saving?
Disclaimer
This post is not to be considered as financial advice or UK tax advice. This is for educational purposes only. Investment returns do vary and this is an illustrative example. When you invest your capital is at risk.
What is Coast FIRE?
Coast FIRE is the point where you’ve saved enough that your investments can grow on their own all the way to a full retirement pot without you ever adding another penny.
Think of it like pushing a snowball over the top of the hill. Once it starts rolling down, gravity does the rest.
When you hit your Coast FIRE number, you don’t need to keep saving for retirement; you just need to cover your bills.
That opens up the whole world of options like: dropping to part-time, switching careers, taking a lower-paid job you actually enjoy or building a side hustle without the financial pressure.
It’s not full financial independence, but it might be the most life-changing milestone you can hit.
For more detailed information on how Coast FIRE works and the necessary calculations, take a look at Coast FIRE – The Complete Guide to Financial Independence.
UK Coast FIRE Calculator
How to Calculate Your Coast FIRE Number
The Coast FIRE Formula (Plain English)
The maths behind Coast FIRE isn’t complicated once you break it down into two steps.
Step 1: Work out your Full FIRE number
This is the total pot you need to retire fully. Take your expected annual spending in retirement and divide it by your safe withdrawal rate. 7% is based on historic market performance of global index fund investments.
Most people use 4% as their safe withdrawal rate. So if you want £30,000 a year in retirement:
£30,000 ÷ 0.04 = £750,000 Full FIRE number
Step 2: Discount that back to today
Your investments grow over time. So you don’t need £750,000 today – you need whatever amount, invested now at 7% growth, will reach £750,000 by the time you retire.
Coast FIRE Number = Full FIRE Number ÷ (1 + growth rate)^years to retirement
For a 35-year-old targeting retirement at 67 with £30,000/yr spending:
£750,000 ÷ (1.07)^32 = £82,000 Coast FIRE number
Once you’ve got £82,000 invested at 35 and leave it alone until 67, it grows to £750,000 on its own. You’re coasting.
That’s what the calculator does automatically – but it helps to know the logic behind the number.
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How To Use The Coast FIRE Calculator
If you’re looking to achieve financial freedom earlier than expected, CoastFIRE might be the perfect solution for you.
The idea behind it is to generate enough wealth to support you in your retirement without further contributions.
I’ve made this calculator to show you how Coast FIRE is possible.
Entering the correct fields will allow you to visualise how close you are to CoastFIRE and what it would take to get to full FIRE.
Follow this list below to understand how each section is interacting with each other.
- Start by selecting your currency this calculator is made for US dollars, British Pounds and Euros.
- Enter your current age and your desired retirement age
- Then enter your current invested net worth so this is all the investments that you have in your ISA. This doesn’t include things like savings as the growth rate will be different.
- You can then change how much your investments are going to grow using the investment growth rate slider.
- After this add in your expected annual spending in retirement this number should be what you need to live comfortably but
- Then set the inflation rate, the average is 2.5-3%.
- And lastly, your safe withdrawal rate which most experts suggest to be around 4%.
How Much Do I Need to Coast FIRE? (By Age)
Not sure if your number is realistic? Use these tables as a rough sense check.
Your numbers will differ – use the calculator above to get your exact figure.
Coast FIRE Numbers by Age
Assumes £30,000/yr retirement spending · 4% safe withdrawal rate · 7% annual growth · retirement at 67
| Age | Years to 67 | Coast FIRE Number | Full FIRE Number | Stage |
|---|---|---|---|---|
| 25 | 42 | £750,000 | Time is your biggest asset | |
| 28 | 39 | £750,000 | Time is your biggest asset | |
| 30 | 37 | £750,000 | Early momentum building | |
| 32 | 35 | £750,000 | Early momentum building | |
| 35 | 32 | £750,000 | Career earnings accelerating | |
| 38 | 29 | £750,000 | Career earnings accelerating | |
| 40 | 27 | £750,000 | Strong compound growth window | |
| 42 | 25 | £750,000 | Strong compound growth window | |
| 45 | 22 | £750,000 | Mid-career push | |
| 48 | 19 | £750,000 | Final sprint to coast | |
| 50 | 17 | £750,000 | Final sprint to coast |
* Full FIRE Number is £750,000 across all ages (based on £30,000/yr ÷ 4% SWR). The Coast FIRE Number falls with age because younger investors have more years for compounding to do the heavy lifting. Use the calculator above for your exact figures.
The biggest takeaway here? Starting early makes an enormous difference.
A 25-year-old needs to have £around £68,000 invested to coast.
A 45-year-old needs nearly five times that amount to achieve the same outcome.
That’s not a criticism of anyone who starts late – it’s just the maths of compounding. Which is exactly why getting started matters more than getting it perfect.
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Coast FIRE Numbers by Lifestyle
The biggest variable in your Coast FIRE number isn’t your age – it’s how much you plan to spend in retirement.
Here’s what the numbers look like for a 35-year-old targeting retirement at 67, depending on their lifestyle.
Your numbers will differ – use the calculator above to get your exact figure.
Coast FIRE Numbers by Lifestyle (Age 35)
How your retirement spending target changes your Coast FIRE number · 4% safe withdrawal rate · 7% annual growth · retirement at 67
| Retirement Lifestyle | Annual Spending | Coast Number at 35 | Full FIRE Number | Gap Still to Close |
|---|---|---|---|---|
|
Lean
Frugal lifestyle, low cost area
|
£20,000/yr | £57,400 | £500,000 |
£442,600 to go
|
|
Moderate
Average UK household, no frills
|
£25,000/yr | £71,800 | £625,000 |
£553,200 to go
|
|
Comfortable
Regular holidays, eating out often
|
£30,000/yr | £86,100 | £750,000 |
£663,900 to go
|
|
Relaxed
No compromises, generous day-to-day
|
£40,000/yr | £114,700 | £1,000,000 |
£885,300 to go
|
|
Fat FIRE
Everything you want, no trade-offs
|
£60,000/yr | £172,100 | £1,500,000 |
£1,327,900 to go
|
* Figures calculated for a 35-year-old targeting retirement at 67 · 4% safe withdrawal rate · 7% annual growth · all figures in today's money. The "Gap to Close" is how much more your invested pot needs to grow from your Coast FIRE number to reach full financial independence. Use the calculator above to get your personalised figures.
If you’re not sure what you’ll spend in retirement, £25,000-£30,000 is a good starting point for most UK households. That covers bills, food, a car, and a couple of holidays a year – but not much luxury.
The important thing is to pick a number and start. You can adjust as life changes.
Coast FIRE for Couples
If you’re planning your finances as a couple, your Coast FIRE number is simply the combined pot you both need – and you can split responsibility for it however makes sense.
The table below assumes a combined retirement lifestyle of £45,000 per year. That’s roughly £3,750 a month between two people – a comfortable but not extravagant retirement.
The ‘monthly each’ column assumes neither of you has anything saved yet and you’re both making a 5-year push.
💑 Coast FIRE for Couples
Combined retirement target of £45,000/yr · 4% safe withdrawal rate · 7% annual growth · retirement at 67 · split 50/50 between partners
| Age | Years to 67 | Combined Coast Number | Each Person Needs | Monthly Each (5-yr push from £0) |
|---|---|---|---|---|
| 25 | 42 | £65,600 | £32,800 each | £471 /mo each |
| 28 | 39 | £80,400 | £40,200 each | £578 /mo each |
| 30 | 37 | £92,100 | £46,100 each | £663 /mo each |
| 32 | 35 | £105,400 | £52,700 each | £758 /mo each |
| 35 | 32 | £129,100 | £64,600 each | £929 /mo each |
| 38 | 29 | £158,100 | £79,100 each | £1,138 /mo each |
| 40 | 27 | £181,100 | £90,600 each | £1,303 /mo each |
| 42 | 25 | £207,300 | £103,700 each | £1,492 /mo each |
| 45 | 22 | £254,000 | £127,000 each | £1,828 /mo each |
* Combined retirement spending of £45,000/yr (£3,750/month between two people) · 4% safe withdrawal rate · 7% annual growth · retirement at 67. Monthly contribution assumes starting from £0 with a 5-year push. You don't have to split 50/50 — if one partner earns significantly more, or is a higher-rate taxpayer, it often makes sense to weight contributions accordingly. Use the calculator above to run your own numbers.
A few things worth knowing for couples:
- You don’t have to split it 50/50. If one of you earns significantly more, it often makes sense to load more contributions on the higher earner – especially if they’re a higher-rate taxpayer who benefits more from pension relief.
- Count your pensions separately. Each person’s workplace pension and ISAs are individual assets. The calculator above works best per person, then add the two numbers together.
- Factor in the State Pension for both of you. The full new State Pension is £12,570/yr each (2026/27). If you’re both on track for the full amount, that’s £25,000+/yr of guaranteed income – which significantly reduces how much your invested pot needs to cover.
Should You Include UK Pensions In Coast FIRE Calculations?
Which Pots Should You Include in Your Coast FIRE Number?
This is the question most UK Coast Fire calculators ignore – and it matters more than people think.
Not all assets grow at the same rate.
And some (like your State Pension) aren’t a pot at all – they’re an income stream.
Here’s how to think about each one:
🇬🇧 UK Pensions & Coast FIRE — What Should You Count?
Not all assets grow the same way. Here's exactly what to include in your Coast FIRE number — and what to leave out.
| Pension / Asset Type | Include It? | What You Need to Know |
|---|---|---|
|
Workplace Pension
(defined contribution) |
✓ Yes | Count the full current value. Your workplace pension compounds just like a Stocks & Shares ISA — in fact it's often your fastest-growing pot because your employer is adding money too. 💡 Check your pension dashboard or ask HR for your current pot value. Don't guess. |
|
Stocks & Shares ISA
|
✓ Yes | Your most flexible pot — include the full value. Unlike a pension, there's no age restriction on withdrawals, so it's essential if you're planning to retire before 57. 💡 If you're aiming for early retirement, your ISA does the heavy lifting until you can access your pension. |
|
State Pension
|
~ Partial | Don't add it to your pot — it's an income stream, not a lump sum. Instead, use it to reduce your target spending. The full new State Pension is £12,570/yr (2026/27). If you're on track for the full amount, that's £12,570 less your investments need to cover each year. 💡 Check your State Pension forecast at gov.uk/check-state-pension — your actual entitlement may be less if you have gaps in your NI record. |
|
Defined Benefit / Final Salary Pension
|
~ Partial | Like the State Pension, treat this as an income stream rather than a pot value. Work out the annual income it'll pay and subtract it from your retirement spending target. The remainder is what your invested assets need to cover. 💡 Example: DB pension pays £8,000/yr, you want £30,000/yr — your investments only need to cover £22,000/yr. That drops your Full FIRE number from £750k to £550k. |
|
Lifetime ISA (LISA)
|
✓ Yes | If you're using it for retirement (not a first home), count it in full. The 25% government bonus makes the LISA one of the best retirement tools available to under-40s. You can access it penalty-free from age 60. 💡 You can only open a LISA if you're under 40, and you can only contribute until you're 50. Max £4,000/yr with a £1,000 government top-up. |
|
SIPP (Self-Invested Personal Pension)
|
✓ Yes | Count the full current value, same as a workplace pension. SIPPs give you more investment choice — particularly useful if your workplace pension has limited fund options or high fees. 💡 Self-employed? A SIPP is likely your main retirement vehicle. You still get tax relief on contributions — basic rate taxpayers get 20% added automatically. |
|
Cash Savings / Easy Access
|
✗ No | Leave cash savings out of your Coast FIRE number. The growth rate on cash is far lower than invested assets — plugging a 4–5% savings rate into a calculator assuming 7% investment growth will give you a misleadingly low Coast FIRE number. 💡 Keep cash savings as your emergency fund (3–6 months of expenses). Everything above that is better off invested. |
|
Property / Buy-to-Let
|
~ Maybe | Complicated. If you plan to sell property and invest the proceeds before retirement, you can include an estimated future value. If you're relying on rental income in retirement, treat it like a DB pension — deduct the income from your spending target instead. 💡 Most people keep property separate from their Coast FIRE number and treat it as a bonus rather than building their plan around it. |
* This table is for educational purposes only and does not constitute financial advice. Pension rules and allowances change — always check current figures at gov.uk or speak to a regulated financial adviser for personal guidance.
The practical approach most people take is this: include your S&S ISA and any defined contribution pensions in the calculator as your ‘current invested assets’.
Then use your State Pension forecast separately to reduce your target spending figure.
So if you want £30,000/yr in retirement but you’re on track for the full State Pension (£12,570), your investments only need to cover £17,430/yr. That drops your Full FIRE number from £750,000 to £462,450 – which changes everything.
You can check your State Pension forecast on the Gov website.
Why does inflation affect Coast FIRE?
Here’s a simple way to think about inflation: the £30,000 you need to live on today won’t buy the same things in 20 years.
When the UK hit 11% inflation in late 2022, your retirement pot needed to be worth 11% more overnight – just to stand still.
That’s the risk.
The calculator handles this for you by letting you set an inflation rate (the UK historical average is around 2–3%).
What it does is adjust your future spending target upwards so your retirement pot is sized in real terms, not just nominal ones.
This matters most for people who are a long way from retirement.
A 25-year-old planning for a 67-year retirement has 42 years of inflation to account for.
At 2.5% inflation, £30,000 today is equivalent to around £83,000 in 42 years’ time.
Leave inflation at zero and your coast FIRE number will look much more achievable than it actually is.
Keep it at 2.5-3% and you’re planning properly.
What else do I need to consider about Coast Fire?
What Can Go Wrong With Coast FIRE Plans?
Coast FIRE is a genuinely useful milestone – but there are a few things that can knock the plan off course.
Markets don’t grow at 7% every year.
That 7% figure is a long-run average. In reality, markets crash, recover, and crash again. A bad decade early in your coast period (called sequence of returns risk) can mean your pot doesn’t compound the way the calculator predicted. The fix? Don’t obsess over a single number. Review your position every year or two and adjust if needed.
Life expectancy is longer than most people plan for.
The UK average life expectancy is now around 81 years – and if you’re in good health at 60, you should plan for 90+. If your pot runs dry at 85, that’s a problem. Build in a buffer, or plan to use your State Pension as your income floor.
Lifestyle creep changes your retirement spending number.
You set your target at £30,000/yr aged 30. Then you get promoted, upgrade your lifestyle, and suddenly £30,000 feels tight. Your Coast FIRE number needs to reflect what you’ll actually spend – not what you thought you would spend a decade ago. Revisit it every few years.
The rules change.
Tax laws, ISA allowances, pension access ages – all of these have changed in recent years and will change again. The minimum pension access age is rising from 55 to 57 in 2028. That doesn’t break Coast FIRE plans, but it’s worth factoring in if you were planning to access your pension early.
None of these are reasons not to aim for Coast FIRE.
They’re just reasons to treat your plan as a live document rather than a set-and-forget number.
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