What is a FIRE number?

A FIRE number is an estimate of how much invested capital you would need to support your chosen level of annual spending, without relying on paid work. It is usually calculated by dividing your annual spending by a long-term withdrawal rate (for example, £40,000 ÷ 4% = £1,000,000). This calculator estimates your FIRE number based on the assumptions you select.

Is the 25× rule accurate in the UK?

The 25× rule is a rough starting point rather than a guarantee. It comes from US-based historical data and assumes a 4% withdrawal rate. In the UK, the rule can still be useful, but outcomes depend heavily on asset allocation, investment returns, taxes, pension access timing, and flexibility in spending. This calculator lets you explore different withdrawal rates rather than relying on a fixed rule.

What withdrawal rate should I assume?

There is no single "correct" withdrawal rate. Common assumptions range from around 3% to 4%, depending on time horizon, risk tolerance, and flexibility. Lower rates reduce risk but require more capital. Higher rates reduce the FIRE number but increase sensitivity to poor market conditions. This calculator allows you to adjust the rate to see how outcomes change.

Does this calculator include pensions, ISAs, or tax?

This calculator focuses on overall investable capital and spending needs, rather than modelling specific tax wrappers in detail. You can include pension and non-pension savings in your total invested assets, but the calculator does not optimise for tax or model drawdown rules. It is designed for high-level planning and comparison, not personalised tax advice.

Is the 4% rule safe in the UK?

The 4% rule is best understood as a historical guideline, not a promise. It was based on specific market conditions and time periods and does not account for future uncertainty. In practice, outcomes depend on market returns early in retirement, spending flexibility, asset mix, and length of retirement. This calculator is designed to explore ranges and scenarios, not to predict a guaranteed outcome.

Where can I learn more about FIRE and how it works in the UK?

If you want a deeper explanation of FIRE, different FIRE approaches, and UK-specific considerations, see our full FIRE guide , which explains the concepts behind the numbers and how people apply them in practice.

FIRE Calculator UK
How Early Could You Retire?

How much do I need to retire early in the UK?

This calculator estimates your FIRE number — the investment pot designed to support your chosen spending level based on assumptions commonly used in UK retirement planning today — and how long it might take to reach it.

Scope: This gives a high-level FIRE number using the 25× rule. For a more detailed plan that models pension tax, ISA/GIA split and State Pension, use our Detailed Retirement Planner.

These tools use mathematical models to illustrate the outcomes generated from the information you enter. Because in the real world markets, tax rules, and personal circumstances can change, the model's results should be viewed as possibilities rather than guarantees. The tools provide projections, comparisons, and potential implications only, and do not constitute personalised advice or recommendations. For specific guidance on investment, pension, or mortgage product decisions, please speak with an FCA-authorised financial adviser. Read full disclaimer

I have read and understand this disclaimer

Start FIRE Calculation

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Your FIRE Estimate

Enter your details, then press Calculate to see your FIRE number and timeline.

Example figures — edit them, then press Calculate.

Your age

Annual spending (today's money)

Current investments (combined)

Monthly savings

Long-term return assumption

5.0%

3%9%15%

Withdrawal rate assumption

Important Limitations

This is a foundational estimate using the 25× rule. Real outcomes depend on tax, fees, market volatility, inflation, and your personal circumstances.

Example figures — press Calculate to see yours

Estimated FIRE Number

£750,000

To generate £30,000 per year using a 4.0% withdrawal rate

Projected years

Projected FIRE age

FIRE Readiness

Your plan looks solid under these assumptions

Your FIRE Timeline

Your projection appears here once you press Calculate.

What's Next?

How Much Do I Need?

Split into Pension, ISA, GIA and add State Pension

Explore Calculator

Plan My Savings

Compare strategies and maximise tax efficiency

Explore Calculator

Plan My Drawdown

Model detailed withdrawal strategies for retirement

Explore Calculator

UK FIRE Guide

12 min read

Understand how FIRE works in the UK context with pensions, ISAs, and tax bridges.

Read Guide

How Much Should I Save for Retirement?

8 min read

Learn the 25× rule and strategies to define your retirement savings target.

Read Guide

Pensions Explained

10 min read

A comprehensive guide to UK pensions, tax relief, and contribution strategies.

Read Guide

About the author

Melanie Reed is a fintech and product specialist with 13+ years' experience building mortgage, investment, savings and retirement tools at companies including Aviva, Lendinvest, Money Advice Trust and Luno. She develops calculators and content that simplify complex UK financial decisions, covering pensions, mortgages, tax-efficiency and long-term savings.

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FIRE Calculator UK
How Early Could You Retire?

How much do I need to retire early in the UK?

Before You Begin

Your FIRE Estimate

Important Limitations

Estimated FIRE Number

Your FIRE Timeline

What's Next?

How Much Do I Need?

Plan My Savings

Plan My Drawdown

UK FIRE Guide

How Much Should I Save for Retirement?

Pensions Explained

About the author

Frequently Asked Questions

Feedback