When can you stop saving for retirement?

Most retirement advice assumes you'll save until the day you stop working. But mathematically, that's not how compounding works. There is a crossover point - different for everyone, and precisely calculable - where the pot you already have will grow into a full retirement by itself, and every further pound you save is optional. The FIRE community calls it Coast FIRE. Working out where your crossover sits is one of the most motivating calculations in personal finance, and one of the few with a genuinely happy answer.

The point where compounding takes over

Full financial independence - FIRE - needs a pot big enough to live off today: roughly 25 times your annual spending, from the 4% rule. For £30,000 a year, that's £750,000, and for most people it's decades away. Coast FIRE asks a gentler question: how much do I need today so that the pot becomes £750,000 by my retirement age with no more contributions? You still work until retirement - but only to pay for the life you're living now. The retirement is already funded; it's just still growing.

Picture two lines on a chart. One falls with age: the pot you'd need at each age to coast from there - high when you're older and there's little time left, low when you're young and compounding has decades to run. The other rises: your actual investments. Where they cross is your coast age. Every year you keep saving, the crossing moves closer.

The UK coast numbers, by age

Here is the coast number at each age for a £30,000-a-year retirement at 65 (a £750,000 target at a 4% withdrawal rate), assuming 6% growth and 2.5% inflation - so the discounting uses the real return, about 3.4%, and every figure stays in today's purchasing power:

The table scales in a straight line with your own target: spend £15,000 a year and every figure halves; spend £60,000 and they double. Want to retire at 60 instead of 65? Shift every row five years younger - a 35-year-old aiming at 60 needs the age-40 figure, £323,975. And the note under the maths matters: the discounting must use growth net of inflation. A pot that merely keeps pace with prices buys no more retirement than it does today; only real growth moves you along the curve.

A worked example: coasting at 52

Take a 35-year-old with £100,000 invested, putting away £1,500 a month, aiming to retire at 60 on £30,000 a year. Their coast number today is £323,975 - so they can't stop yet; they're £223,975 short. But keep the £1,500 a month flowing and the rising pot line crosses the falling requirement line at age 52. From that birthday, the maths says every remaining pound of saving is optional: eight years of contributions they could redirect at the mortgage, at working less, at life - while the pot finishes the job on its own.

The two UK catches

• The pension lock. UK pensions can't be touched until 55 today, rising to 57 from April 2028. If most of your pot is pension and you're coasting toward retirement at 55 or earlier, the total being big enough isn't enough - the years before pension access must be covered by ISAs or other accessible investments. A coast plan needs the right pots, not just the right total.
• The employer match. Stopping your workplace pension contribution means refusing your employer's contribution and the tax relief on your own - typically an instant, guaranteed return no investment can match. Reaching your coast number is a reason to stop extra saving, almost never a reason to give up matched money.

What Coast FIRE is actually for

Almost nobody who hits their coast number stops saving the next morning - growth isn't guaranteed, and the model assumes the future cooperates. What the number really buys is options. It converts "I must maximise my income for thirty more years" into "my retirement is handled; the rest is choice": the licence to take the interesting lower-paid job, drop to four days, start the business, or simply stop feeling behind. That psychological shift, backed by real arithmetic, is why Coast FIRE has become the most popular milestone in the FIRE world - it's the first one within ordinary reach.

“Coast FIRE doesn't tell you to stop saving. It tells you that, from here, saving is a choice.”