UK FIRE number calculator

What is the UK FIRE number?

Your FIRE number is the total portfolio value at which your investment returns sustainably cover your annual spending without you needing to earn income. The most common rule of thumb is 25 times your annual expenses (the inverse of a 4% withdrawal rate). For UK residents spending £30,000 a year after tax, that's a £750,000 portfolio. A more conservative 3.5% rate — appropriate for retirements lasting 40+ years — implies a £857,000 target.

ISA: your pre-retirement bridge

A Stocks and Shares ISA lets you invest up to £20,000 per year (2024/25 allowance) with no tax on dividends, interest, or capital gains — ever, including on withdrawal. Crucially, there is no minimum age to withdraw, making the ISA the ideal bridge account for the years between retiring early and being able to access your pension. If you and a partner both maximize ISA contributions over a 10-year career, you could shelter £400,000+ in an entirely tax-free wrapper.

SIPP pension: the tax-boosted long-term pot

A Self-Invested Personal Pension (SIPP) adds 20% tax relief at source on contributions, and higher-rate taxpayers can claim a further 20–25% via their tax return — effectively letting you invest £1,000 for as little as £600. Growth is sheltered from tax inside the wrapper. The catch for early retirees: you cannot access a SIPP until the Minimum Pension Age, currently 55 and rising to 57 in 2028. Plan your ISA bridge accordingly. At drawdown, 25% of the pension pot can be taken tax-free; the remainder is taxed as income, but you can manage annual withdrawals to stay within lower tax bands.

How to use this calculator for UK FIRE

• Set your current balance to the combined value of your ISA and pension (and any general investment account).
• Set your monthly contribution to what you invest across all wrappers each month.
• Set your FIRE target using 25× (4% rule) or 28.5× (3.5% rule) times your annual spending.
• Adjust the return rate. A low-cost global index fund (e.g. HSBC FTSE All World) has historically returned ~7% real. Subtract your fund's OCF (ongoing charges figure).

UK-specific safe withdrawal considerations

The State Pension (currently £11,502/yr at full rate) can significantly reduce how much your portfolio needs to cover from age 67. Many UK FIRE planners build a two-phase model: a higher withdrawal from the portfolio before State Pension age, stepping down once the State Pension kicks in. FirePath's income event feature lets you model exactly this — add a recurring income event starting at age 67 to see how it brings your FIRE date forward.