Coast FIRE Calculator UK
Find out if your ISA and SIPP investments will reach your FIRE number without another penny of contributions.
Your Numbers
Include all investable assets — ISAs, SIPPs, GIAs, and cash savings.
6–7% is typical for global index funds
What Is Coast FIRE?
Coast FIRE is a milestone on the path to full financial independence. You have reached Coast FIRE when your existing investments are large enough that, left to grow untouched, they will reach your full FIRE number by your target retirement age — without any further contributions.
The name comes from the idea that you can now “coast” to retirement. You still need to earn enough to cover your current living costs, but the pressure to save aggressively for the future is gone. Many people find this milestone gives them the freedom to change careers, work part-time, or pursue work they genuinely enjoy.
How Is Coast FIRE Calculated?
Your Coast FIRE number is your full FIRE number discounted back to today at your expected investment return. The formula is:
Coast FIRE Number = FIRE Number ÷ (1 + annual return)^years to retirement
For example: FIRE number of £750,000, 25 years to retirement, 6% annual return. Coast FIRE number = £750,000 ÷ (1.06^25) = £750,000 ÷ 4.29 = approximately £175,000. Once your portfolio hits £175,000 today, it will grow to £750,000 in 25 years without another penny of contributions.
Coast FIRE and UK Tax Wrappers
For UK investors, Coast FIRE works especially well because the most common investment vehicles — ISAs and SIPPs — compound completely tax-free. There are no annual taxes on dividends or capital gains within these wrappers, which means your money grows at the full gross return rate rather than an after-tax rate.
A £175,000 Coast FIRE portfolio in a Stocks and Shares ISA growing at 6% for 25 years reaches approximately £750,000 — entirely free of capital gains tax on the gains. In a taxable account, the same starting portfolio would need to be larger to reach the same after-tax figure.
Frequently Asked Questions
What is Coast FIRE?
Coast FIRE is when your existing investments will grow to your full FIRE number by retirement without further contributions. You still need income for day-to-day costs, but can stop saving for the future.
What return rate should I use for the Coast FIRE calculation?
Most UK FIRE planners use 5–7% as a real annual return for a globally diversified index fund portfolio. 6% is a commonly used middle-ground assumption. Being conservative (5%) gives a safer result; being optimistic (7–8%) reduces the required Coast FIRE number.
Do I include my SIPP in my Coast FIRE portfolio?
Yes — include your SIPP balance in your current portfolio. Note that SIPP funds are not accessible until age 57 (rising from 55 in 2028), so if you plan to retire before 57, ensure you have enough in your ISA to bridge the gap.
What should I do after reaching Coast FIRE?
Options include switching to part-time work (Barista FIRE), moving to a less stressful career, taking a sabbatical, or simply reducing financial anxiety. You still need to cover living costs, but the retirement savings pressure is gone entirely.
This calculator is for illustrative purposes only and does not constitute financial advice. Investment returns are not guaranteed and past performance is not a reliable indicator of future results. For advice specific to your circumstances, consult a qualified financial adviser.
Related Calculators
- UK FIRE Number Calculator — calculate your full FIRE target
- UK Savings Rate Calculator — see how your savings rate affects your timeline
- Safe Withdrawal Rate Calculator — model your retirement income
- All UK FIRE Calculators
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