FIRE Calculator

Calculate your FIRE number using the 4% rule and see how your current portfolio and monthly savings compare. Shows projected portfolio at your target retirement age and years to financial independence.

Last updated: April 2026

Your FIRE details
The annual amount you need to live on in today's money.
4% is the classic rule. 3–3.5% is more conservative for very early retirement.
Current position
FIRE number & progress
Your FIRE number
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Current portfolio -
Projected at target age -
Surplus / shortfall -
% of FIRE number achieved -
Years to FIRE (at current rate) -
Monthly income from FIRE number -

What is FIRE?

FIRE stands for Financial Independence, Retire Early. The concept centres on building a portfolio large enough that investment returns alone can sustain your lifestyle indefinitely - without ever needing paid employment again. The key calculation is your FIRE number: the total portfolio value needed, which is your annual spending divided by your safe withdrawal rate. At a 4% withdrawal rate, the FIRE number is 25 times your annual spending.

The 4% rule

The 4% rule comes from the Trinity Study (1998), which found that a portfolio of 50–75% equities could sustain a 4% annual withdrawal for 30 years in almost all historical market scenarios. The rule assumes the portfolio is invested in a diversified equity/bond mix, that withdrawals are inflation-adjusted each year, and that the time horizon is around 30 years. For very early retirees with a 40–50 year horizon, a 3–3.5% withdrawal rate is more conservative and commonly recommended. Each 0.5% reduction in withdrawal rate increases the required FIRE number by approximately 14%.

Coast FIRE and Lean FIRE

There are several variants of FIRE worth knowing. Coast FIRE is the point at which your existing portfolio - if left to grow without further contributions - will reach your full FIRE number by a standard retirement age. Reaching Coast FIRE means you can stop saving aggressively and just cover living costs from income. Lean FIRE means retiring on a minimal budget (under £20,000 per year in the UK). Fat FIRE targets a comfortable lifestyle (£40,000+ per year). Barista FIRE means having enough invested to reduce working hours to part-time, with a small income covering the gap.

Frequently asked questions

The savings rate needed for FIRE depends on your target timeline. Saving 10–15% of income (the typical advised level) will take 30–40 years to reach a standard FIRE number. Saving 40–50% of income compresses the timeline to 15–20 years. Saving 60–70% of income - aggressive but achievable for high earners with modest lifestyles - can achieve FIRE in 10–12 years. The relationship between savings rate and time to FIRE is non-linear: doubling your savings rate more than halves the time, because you are simultaneously reducing your spending (and thus the FIRE number) while growing the portfolio faster.
For UK residents, the State Pension (£11,502/year in 2026/27) becomes available at 67. If you retire early at 50, you have 17 years before State Pension income begins. Many FIRE calculators treat the State Pension as a supplement that reduces the portfolio drawdown required from age 67 onwards - reducing the needed portfolio size. To qualify for the full new State Pension you need 35 qualifying NI years. Early retirees may want to pay voluntary Class 3 NI contributions (£956.80 per year in 2026/27) to fill gaps and secure the full entitlement.
Ideally both, structured for tax efficiency. A pension is typically the most tax-efficient vehicle for accumulation (full tax relief on contributions, employer matching) but cannot be accessed until age 57. An ISA provides tax-free growth and income with no access restrictions. A common FIRE strategy is to build a bridge portfolio in ISAs to fund the years between early retirement and pension access age, while the pension grows in the background. Using both wrappers maximises tax efficiency across the full accumulation and drawdown phase.

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