What Coast FIRE means and why it matters
FIRE stands for Financial Independence, Retire Early: building an invested pot big enough to fund your spending for the rest of your life. Most people picture it as a single finish line. Coast FIRE adds an earlier milestone. It is the point where what you have already invested will grow into that full pot by your chosen retirement age without another penny added. You still have to cover your living costs until then, but you no longer have to save for retirement on top.
That shift changes the choices open to you. Someone who has reached Coast FIRE can take a lower-paid job they enjoy more, go part-time, take a career break or start a business, knowing their retirement is on course as long as they leave the investments alone. The FIRE calculator tells you how long the full journey takes with regular saving. This page answers a narrower question: how much do I need invested today to be able to stop?
Worked example: 30 years old, retiring at 60
Priya is 30 and would like to stop working at 60. She expects to spend £30,000 a year in today's money and plans on a 4% withdrawal rate, so her FIRE number is £30,000 ÷ 0.04 = £750,000. She has £60,000 across her workplace pension and a Stocks and Shares ISA, and she assumes a 7% real return.
Her money has 30 years to grow, and at 7% a pound invested today becomes about £7.61 by then. Dividing £750,000 by 7.61 gives a Coast FIRE number of about £98,500. Priya is roughly £38,500 short. Left alone, her £60,000 would grow to about £457,000 by 60, well below her target. She would reach £750,000 without any more contributions only at about 67. To still retire at 60, she needs to invest about £251 a month from now on. That is less than many people expect, because the earliest pounds do most of the work.
Now run the same numbers at a 5% real return instead of 7%. Her Coast FIRE number almost doubles to about £173,500, and the monthly saving needed to retire at 60 rises to about £602. The return you assume matters far more than any other input, which is why it is worth checking a cautious figure alongside an optimistic one.
UK rules that change the picture
Two UK rules matter when you retire early. First, you normally can't take money from a private or workplace pension until the minimum pension age, which rises from 55 to 57 on 6 April 2028. If your Coast FIRE retirement age is earlier than that, part of the pot needs to sit in ISAs or a general investment account that you can reach sooner. Second, the State Pension starts later still. It is currently paid from 66, rising to 67 between 2026 and 2028. At the full 2026/27 rate of £12,548 a year, it can cover a large share of a modest budget. Many UK planners therefore split their target into two parts: a bridge pot for the years before State Pension age, and a smaller long-term pot for the gap the State Pension leaves.
Tax wrappers help a Coast FIRE plan because there is nothing to sell or report while the money grows. Pension contributions get tax relief on the way in, and growth inside an ISA is tax-free on the way out. A pot that compounds untouched in either wrapper keeps the full return instead of losing part of it to tax each year. That matters most over the long stretches this calculator models.
Mistakes to avoid
The most common mistake is treating Coast FIRE as a guarantee. The calculation assumes a steady return every year, but real markets move in uneven sequences. A bad decade just after you stop contributing leaves less time to recover. Check your finished plan with the retirement drawdown simulator, which tests withdrawals against every real market period since 1957. The second mistake is counting money that won't stay invested: your home, emergency cash or savings set aside for a house deposit. The third is forgetting to revisit the numbers. If your spending plans rise, your FIRE number rises with them, and so does the Coast number you need today.
If you are short of Coast FIRE, the monthly saving figure shows the most direct way to close the gap. To see how regular contributions compound over time, and how much daily or monthly compounding adds, try the compound interest calculator.
For education only, not financial advice. Projections assume a constant real return and withdrawal rate; actual returns vary year to year and are not guaranteed. State Pension figures are from GOV.UK for 2026/27, and the minimum pension age change is set out in the Finance Act 2022. Consider speaking to a regulated financial adviser before making retirement decisions.