UK FIRE Number Calculator

What Is a UK FIRE Number?

Your FIRE number is the total invested portfolio you need to retire early and sustain your lifestyle indefinitely from investment returns. The standard calculation is simple: divide your annual expenses by your safe withdrawal rate. At 4%, that means multiplying annual expenses by 25. Spend £30,000/year? Your FIRE number is £750,000.

But in the UK, the headline number is often misleading — because most UK FIRE planners will eventually receive the State Pension and benefit from the NHS, both of which dramatically reduce what your portfolio actually needs to do.

How the UK State Pension Reduces Your FIRE Number

The full UK State Pension is £11,502/year (2025/26), payable from age 67 with 35 qualifying National Insurance years. For a couple where both partners receive the full State Pension, that is £23,004/year in guaranteed, inflation-linked income — enough to cover many households' basic costs entirely.

At a 4% withdrawal rate, £11,502/year of State Pension is equivalent to having £287,550 more in your portfolio. For a couple, that is a combined £575,100 reduction in required portfolio. This is why UK FIRE numbers are often substantially lower than equivalent US numbers despite similar expenses.

If you are retiring early — say at 45 — you need enough portfolio to bridge the gap between retirement and age 67 when State Pension begins. The bridge FIRE number in this calculator accounts for that gap properly, rather than simply dividing by 4%.

The NHS Advantage: Why UK FIRE Numbers Are Lower

US FIRE planners must budget for private health insurance from retirement until Medicare begins at 65 — commonly £12,000–£20,000 per year for a couple. Over a 20-year early retirement, that is £240,000–£400,000 in healthcare costs that UK early retirees simply do not face.

At a 4% withdrawal rate, eliminating £15,000/year of healthcare costs reduces the required FIRE number by £375,000. Combined with the State Pension advantage, UK FIRE is structurally more achievable than the US equivalent — even accounting for higher property costs and lower average salaries.

Which Accounts Count Towards Your FIRE Number?

All investable assets count towards your FIRE number, but the tax treatment differs by account type:

• Stocks and Shares ISA: Withdrawals are completely tax-free. Count the full balance — this is the most valuable account type for FIRE drawdown.
• SIPP: 25% can be taken tax-free (up to £268,275 lifetime limit) from age 57. The rest is taxed as income. Count the full balance but plan for tax on SIPP withdrawals.
• GIA (General Investment Account): Subject to Capital Gains Tax on gains above £3,000/year. Count the full balance but plan for CGT.
• Cash savings: Count as part of your FIRE number but earn less than invested assets — typically used for your emergency fund or near-term spending.

4% Rule or 3.5% for UK Early Retirees?

For a 30-year retirement, the 4% rule (25× expenses) is historically well-supported. For a 40+ year retirement — common for those retiring in their 40s — many UK planners prefer 3.5% (28.5× expenses). The difference is significant: at £30,000 annual expenses, switching from 4% to 3.5% increases the required portfolio by £105,000.

One approach used in the UK FIRE community: use 4% for the period after State Pension begins (a shorter, lower-risk phase) and 3.5% for the bridge period before it. This gives a more nuanced and accurate FIRE number than applying a single rate across the entire retirement.

Frequently Asked Questions

This calculator is for illustrative purposes only and does not constitute financial advice. Tax rules, State Pension amounts and allowances can change. The 4% rule is based on historical data and does not guarantee future results. For advice specific to your circumstances, consult a qualified financial adviser. State Pension figures are based on 2025/26 rates.

Related Calculators

• UK Safe Withdrawal Rate Calculator — model your annual withdrawals
• Coast FIRE Calculator UK — find out if you can stop contributing now
• UK Savings Rate Calculator — see how your savings rate affects your FIRE date
• All UK FIRE Calculators