"How is the UK FIRE number calculated?"

"FIRE number = Annual spending ÷ Safe withdrawal rate. At a 4% withdrawal rate, you need 25× your annual spending. This calculator adjusts for state pension, DB pension income, and inflation to give you a more accurate UK-specific figure."

"Does the state pension count towards my FIRE number?"

"Yes — if you're retiring before state pension age (67), your pot must cover full spending until then. If retiring at or after 67, your pot only needs to cover spending minus the state pension of £11,502/yr (2024/25 rate). This calculator handles both scenarios."

"What safe withdrawal rate should I use in the UK?"

"4% is the classic rate from the Trinity Study (US research). For UK investors with a potentially longer retirement, 3.5% is more conservative. This calculator lets you choose 3.5%, 4% or 4.5%."

FIRE Number Calculator UK — What's Your Magic Number?

Q: "What is a FIRE number?"

"Your FIRE number is the total invested pot you need to retire early. It's calculated by dividing your annual spending by your safe withdrawal rate (typically 4%). If you plan to spend £25,000 per year, your FIRE number is £625,000."

What Is a FIRE Number?

Your FIRE number is the total invested pot that, once reached, means work becomes optional. It’s the cornerstone concept of the FIRE movement — Financial Independence, Retire Early.

The formula is elegantly simple:

FIRE number = Annual retirement spending ÷ Safe withdrawal rate

At the classic 4% safe withdrawal rate, you need 25× your annual spending. Spend £25,000 per year? Your FIRE number is £625,000.

How This Calculator Works

This calculator projects your pot growth in real (inflation-adjusted) terms — so all the numbers you see are in today’s purchasing power. That means:

The FIRE number line on the chart stays flat (it’s a constant in today’s money)
Your pot growth accounts for inflation eating into returns
Monthly savings are assumed to be constant in real terms

Inputs you control:

Input	What it means
Current pot	Everything invested today — ISA, pension, GIA
Monthly savings	Your regular contribution across all accounts
Annual spending	What you plan to spend each year in retirement
State pension	£11,502/yr from age 67 (2024/25 rate)
Growth rate	Expected nominal annual return (7% is UK market average)
Withdrawal rate	% of pot withdrawn per year (4% is the classic “safe” rate)

The 4% Rule — Does It Work in the UK?

The 4% rule comes from the Trinity Study (1998), which found a 4% withdrawal rate survived virtually all 30-year periods in US market history. For UK investors:

UK market returns have been broadly similar to US over long periods
Sequence-of-returns risk is the main danger — a crash early in retirement can be devastating
Many UK FIRE retirees use 3.5% for extra safety, especially for retirements of 40+ years

Read our full guide to the 4% rule →

What About the State Pension?

The UK state pension (currently £11,502/yr) is a significant income source — but it doesn’t start until age 67 (rising to 68 by 2046). If you retire at 55, your pot must cover full spending for 12 years before any state pension kicks in.

This calculator handles this correctly: if your target retirement age is before 67, the FIRE number is calculated conservatively (full spending / SWR), then the summary notes how much easier things get once state pension starts.

ISA vs SIPP — Does It Matter?

Both ISAs and SIPPs (Self-Invested Personal Pensions) are tax-efficient wrappers for your investments. The key difference for FIRE planning:

ISA — accessible any time, tax-free growth and withdrawals
SIPP — 25% tax-free lump sum, rest taxed as income, accessible from age 57 (rising to 57 in 2028)

If retiring before 57, you need sufficient ISA/GIA savings to bridge the gap until pension access. Many UK FIRE savers use a “bucket strategy” — ISA savings for early years, SIPP for later.