FIRE Calculator (UK)
Can you retire early? Work out your FIRE number from annual spending and a withdrawal rate (e.g. 4%), then see how many years your portfolio and monthly contributions might take to get there.
Your plan
Investable assets (ISAs, GIA, pensions you count toward FIRE).
Illustrative only. Long-run equity-heavy portfolios are often modelled around 6–8% nominal before inflation.
Spending & withdrawal
What you plan to spend per year from your portfolio (today’s money).
The 4% rule is a common starting point; lower rates are more conservative for long retirements.
Your FIRE outlook
FIRE number (target portfolio)
£1,000,000
Spending £40,000/yr ÷ 4.00% withdrawal
Progress to FIRE
25.00%
of target
Years to FI
14
Indicative retirement age (at FI)
49
If you retired today
At a 4.00% withdrawal rate, your portfolio could support about £10,000 per year (illustrative, not advice).
You need £750,000 more to reach your FIRE number at current spending.
Withdrawal rate quick reference
| Rate | FIRE number for £40k/yr spending | Note |
|---|---|---|
| 3% | £1,333,333 | More conservative |
| 3.5% | £1,142,857 | Middle ground |
| 4% | £1,000,000 | Classic “4% rule” |
| 4.5% | £888,889 | Higher risk of running short |
UK FIRE: pensions & ISAs
ISAs
Stocks & Shares ISAs grow tax-free and can be withdrawn any time—useful for bridging years before pension age. Annual allowance £20,000.
Pensions
Pensions get tax relief on the way in but are usually locked until minimum pension age (55+, moving to 57 for many). Often used for later years of a long retirement.
Related calculators
Frequently asked questions
Can I retire early in the UK?
Whether you can retire early depends on whether your investments can support your spending for life. A common rule of thumb is the “4% rule”: in retirement you withdraw 4% of your portfolio in year one, then adjust for inflation. Your “FIRE number” is annual spending divided by that withdrawal rate (e.g. £40,000 spending ÷ 4% = £1,000,000). This is a simplification, not a guarantee—markets and your life will differ.
What is the 4% withdrawal rule?
The 4% rule comes from historical research (often called the Trinity study) on US portfolios. It suggests that withdrawing about 4% of your initial portfolio in year one, then increasing withdrawals with inflation, may last 30 years in many historical scenarios. Some people use 3% or 3.5% for extra safety, especially for longer retirements or UK-only portfolios.
What is a FIRE number?
Your FIRE number is the portfolio size you aim for so that your chosen withdrawal rate covers your annual spending. Formula: spending ÷ withdrawal rate. So £40,000 a year at 4% implies a £1 million portfolio.
Does this include tax?
No. Returns are shown gross. In practice, ISAs grow tax-free; pensions have tax relief going in and tax on withdrawals. Use a tax adviser or detailed modelling for your situation.
How does the UK pension system affect FIRE?
Private pensions (including workplace pensions) are usually accessible from age 55 (rising to 57 for some). The State Pension starts at State Pension age (66–68 depending on age). Many UK FIRE plans use ISAs for early years before pension access, and pensions for later years. This calculator does not model separate accounts separately.
What is lean FIRE vs fat FIRE?
Lean FIRE means lower annual spending and a smaller FIRE number. Fat FIRE means higher spending and a larger portfolio. The same calculator applies—just change your spending and withdrawal rate.