Coast FIRE in the UK: what it means
Coast FIRE is the moment you have enough invested that, even if you never add another pound, ordinary compound growth will grow your pot to your full retirement number by the time you stop work. You still pay for today's life out of your income, but you no longer need to save for retirement — it is already on track. For UK investors, the concept fits neatly around the accounts you already hold: your workplace and personal pensions (including SIPPs), your Stocks and Shares ISA, and any general investment account, all compounding in the background while you ease off saving.
This page runs the same inflation-adjusted Coast FIRE maths as our main calculator, but with amounts in pounds sterling and the discussion framed around UK accounts and the State Pension. Enter your figures above to see your FIRE number, the amount you need invested today to coast, and the age you can stop contributing.
How the Coast FIRE number is calculated
Begin with your full FIRE number: your desired annual retirement spending divided by your safe withdrawal rate. The 4% rule implies 25× your spending, though many UK investors planning a long or early retirement prefer a more cautious 3.25%–3.75%. Then discount that target back to today using a real, inflation-adjusted return.
Coast FIRE number today = (annual spending ÷ withdrawal rate) ÷ (1 + r)years to retirement
The calculator uses the precise Fisher relationship for the real return — approximately (1 + nominal return) ÷ (1 + inflation) − 1 — so every figure stays in today's pounds. If your combined pension, ISA and GIA balances already exceed the Coast FIRE number, your retirement is effectively self-funding.
Pensions, ISAs and the access-age trap
When you enter your "current invested assets", include the long-term money you control: workplace pensions, personal pensions and SIPPs, your Stocks and Shares ISA, and any general investment account (GIA). A few UK-specific points are worth remembering:
- Pensions can't normally be accessed until 55 (rising to 57 in 2028). If you want to retire earlier than that, your ISA and GIA have to bridge the gap — so where your money sits matters, not just how much there is.
- ISA withdrawals are tax-free, which makes the ISA especially useful both for early-retirement bridging and for managing taxable income later.
- Pension withdrawals are mostly taxable beyond the 25% tax-free lump sum, so your real spending power is a little below the headline balance. Cautious planners haircut the pension slightly for future tax.
- Leave out your emergency fund and the equity in your home — they are not part of the compounding portfolio.
Don't forget the State Pension
Most UK retirees will receive the State Pension, which currently begins at 66 (rising to 67, then 68). That guaranteed income reduces how much your own portfolio must cover. A simple, conservative approach: estimate your expected annual State Pension, subtract it from your target retirement spending, and enter the reduced figure. A smaller spending number means a smaller FIRE number and a smaller Coast FIRE number — which is why leaving out the State Pension makes coasting look harder than it really is. Checking your forecast on the government's State Pension service is a quick way to firm up the estimate.
Healthcare: less of a hurdle than in the US
A real advantage of coasting in the UK is the NHS. Where American early retirees fixate on bridging private health cover to age 65, UK residents are covered for core healthcare throughout. You may still want to budget for dental, optical, or private medical insurance if you value faster access, but the catastrophic "what happens to my health cover if I leave my job?" question that dominates US FIRE forums barely applies here. Add a modest line for out-of-pocket health costs and carry on.
Factoring in inflation
UK inflation has varied a lot in recent years, with the Bank of England targeting 2% over the long run. Because Coast FIRE depends on decades of compounding, even a one-point change in your assumed real return shifts the result substantially. This calculator keeps everything in today's pounds and lets you set inflation with a slider, so you can stress-test a higher-inflation environment without guessing what a future pound is worth.
How to use this Coast FIRE calculator (UK)
- Enter your age and target retirement age. The gap is your compounding runway.
- Add your pension, ISA and GIA balances as current invested assets — and note whether you'll retire before pension access age.
- Set your monthly contribution at your current saving pace.
- Estimate annual retirement spending in today's pounds — then, optionally, subtract the State Pension to keep it conservative.
- Tune return, inflation and withdrawal rate, then read your Coast FIRE number and coast age. Export a PDF or copy a share link when you're done.
Frequently asked questions
What is Coast FIRE in one sentence?
Coast FIRE is having enough invested that compound growth alone will reach your retirement number by your target age, so you no longer need to save for retirement — only cover your current living costs.
Does this calculator work for the UK?
Yes. It runs standard inflation-adjusted Coast FIRE maths with amounts in pounds, and the guidance here is framed around pensions, SIPPs, ISAs and the State Pension. The formula is universal; only the accounts and currency differ.
Should I include my pension and ISA together?
Yes — include workplace and personal pensions, SIPPs, your ISA and any GIA as current invested assets. Just remember pensions can't be accessed until 55 (57 from 2028), so if you plan to retire earlier your ISA and GIA need to bridge those years.
How does the State Pension affect my number?
It lowers it. Because the State Pension covers part of your retirement spending, you can subtract your expected annual amount from your target spending before entering it, which reduces both your FIRE number and your Coast FIRE number.
Does it account for inflation?
Yes. It converts your expected return into a real, inflation-adjusted return and keeps every figure in today's pounds, with an inflation slider so you can see how rising prices change your Coast FIRE number.
Is my data private?
Yes. All calculations run entirely in your browser; nothing you enter is sent to a server. The share-link feature only encodes your inputs into a URL you choose whether to share.