"How is the Coast FIRE number calculated?"

"Coast FIRE number = FIRE number ÷ (1 + real growth rate)^years to retirement. For example, with a £625k FIRE number, 20 years to retirement at 4.4% real return, the Coast FIRE number is approximately £272k."

"What happens after you hit Coast FIRE?"

"After hitting Coast FIRE, you no longer need to invest aggressively. You only need to earn enough to cover your current living expenses — the pot grows to your FIRE number on its own. Many people use this phase to downshift to more enjoyable, lower-paying work."

Coast FIRE Calculator UK — Have You Already Won?

Q: "What is Coast FIRE?"

"Coast FIRE is when your invested pot is large enough that — even without any further contributions — it will grow to your full FIRE number by your target retirement age, purely through investment returns."

What Is Coast FIRE?

Coast FIRE is the moment when your invested portfolio is large enough to grow to your full FIRE number by retirement — with no further contributions. You’ve done the hard part. Now you can “coast” to the finish line.

The maths:

Coast FIRE number = FIRE number ÷ (1 + real return)^years to retirement

At 4.4% real return (7% nominal minus 2.5% inflation), with 20 years to retirement and a £625k FIRE number: Coast FIRE number = £625,000 ÷ (1.044)^20 ≈ £272,000

Why Coast FIRE Is a Game Changer

Once you hit your Coast FIRE number, work becomes optional for income accumulation purposes. You still need to pay your current bills — but you don’t need to save a single extra pound for retirement. Your pot does the heavy lifting.

This creates real options:

Downshift: Move to enjoyable part-time or lower-stress work
Career change: Take a lower-paying role you actually love
Parent: One partner stops working to raise children
Take a sabbatical: Travel, study, or just breathe

The freedom comes not from having enough to retire today — but from having enough that you will retire, no matter what.

Coast FIRE vs. Regular FIRE

	Regular FIRE	Coast FIRE
When you hit it	You can retire now	Your pot will grow to retirement by target date
Work optional?	Yes, completely	Optional for saving — still need living expenses
Contribution required	Zero	Zero for retirement — still need income for bills
Typical pot size	Full FIRE number	Fraction of FIRE number
Timeline benefit	Can retire immediately	Freedom to work less/different now

The Coast FIRE Calculation

Use the calculator above to find your exact Coast FIRE number. The key inputs:

FIRE number — your retirement target (annual spending / SWR)
Years to retirement — how long your pot has to grow
Real growth rate — nominal rate minus inflation

The longer you have to retirement, the smaller your Coast FIRE number — because compound growth does more work over longer periods.

Already Hit Coast FIRE?

If your current pot is at or above your Coast FIRE number — congratulations. You’re officially financially “on track” to retire by your target date. The pressure to save aggressively is gone.

Many people discover they’ve hit Coast FIRE without realising it. If you’ve been saving for 10–15 years and your pot has grown meaningfully, run the calculation — you might be closer than you think.

Calculate your full FIRE number →