Question 1

What is a FIRE number?

Accepted Answer

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.

Question 2

Is the 25× rule accurate in the UK?

Accepted Answer

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.

Question 3

What withdrawal rate should I assume?

Accepted Answer

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.

Question 4

Does this calculator include pensions, ISAs, or tax?

Accepted Answer

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.

Question 5

Is the 4% rule safe in the UK?

Accepted Answer

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.

Question 6

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

Accepted Answer

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.

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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

Estimated FIRE Number

FIRE Readiness: On Track

Your FIRE Timeline

Important Limitations

What Level of Confidence Do You Want?

Assumptions & Notes

What's Next?

Plan My Savings

Plan My Drawdown

UK FIRE Guide

How Much Should I Save for Retirement?

Pensions Explained

About the author

Frequently Asked Questions

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