What is the FIRE Number Calculator?
The FIRE Number Calculator helps you work out how much money you need to reach financial independence and retire early in the UK. It calculates your personal FIRE number based on your spending, income and investment mix, then projects when you could realistically reach it using UK-specific accounts and pension rules.
How the Calculator Works?
This calculator starts by calculating your FIRE number using your target annual spending and a chosen safe withdrawal rate. It then adjusts this number to account for guaranteed income such as the State Pension, defined benefit pensions and buy-to-let income.
Using your current savings, pensions and investments, the tool runs a year-by-year projection to show how your wealth accumulates over time. It models UK pension access rules, tests whether early retirement is sustainable, and checks whether you can fund the bridge period before pensions become available. All results are shown in real terms, meaning today’s spending power after inflation.
Step One: Set Your Spending and FIRE Assumptions
Enter your target annual spending and choose a safe withdrawal rate. The calculator uses this to calculate your classic FIRE number and an adjusted FIRE number that includes guaranteed income.
Step Two: Add Your Assets and Income Sources
Enter your cash savings, ISAs, GIAs, SIPPs and workplace pensions, along with State Pension, DB pensions and buy-to-let income. The tool applies UK access rules and income start ages.
Step Three: Review Your FIRE Timeline and Retirement Feasibility
See your FIRE number, progress so far, years to reach FIRE and projected FIRE date. The calculator also shows the earliest sustainable retirement age and whether you can fund the gap before pensions begin.
Disclaimer:
This calculator provides illustrative projections only and does not constitute financial advice. Investment returns, pension rules and personal circumstances can change. Consider speaking with a qualified financial adviser before making major retirement decisions.
What does retirement mean to you?
Traditional retirement is broken. Understand how our calculator enables you to live a better life now vs later.
Retire from corporate work?
Use the tool to utilise how you can step away from the corporate world and live life on your own terms.
Work less, live more
See how part-time or project-based work can bridge your income gap while giving you more time for life.
Freedom through planning
Understand how your savings, spending and investments can work together to buy back your time.
Test-drive retirement early
Model scenarios that let you experience elements of retirement before fully stepping away.
What is the FIRE Number Calculator?
The FIRE Number Calculator is a UK-specific planning tool that calculates how much wealth you need for financial independence and projects when you could realistically retire based on your assets, income and pension rules.
What is a FIRE number?
Your FIRE number is the total amount of invested wealth needed to support your annual spending indefinitely, based on a chosen safe withdrawal rate.
What is the 4% rule?
The 4% rule is a retirement planning guideline that suggests you can withdraw around 4% of your investment portfolio each year, adjusted for inflation, with a high likelihood that your money will last for at least 30 years. It was popularised by financial planner William Bengen in the 1990s, based on historical US market data.
The rule became widely known after the Trinity Study, which tested different withdrawal rates across historical market periods. While the 4% rule is often used as a starting point, it is not a guarantee. Outcomes depend on market returns, inflation, time horizon, spending flexibility and asset allocation.
For UK early retirees or those planning for longer retirements, many people choose more conservative rates such as 3–3.5%, or stress-test higher rates like 5–6% to understand the trade-offs.
What withdrawal rates can I use?
The calculator allows you to test rates such as 3%, 4%, 5% and 6%. Lower rates are more conservative and require a larger FIRE number, while higher rates assume more risk.
What is the difference between classic and adjusted FIRE numbers?
The classic FIRE number is based purely on spending and withdrawal rate. The adjusted FIRE number reduces the required pot by accounting for guaranteed income such as the State Pension, DB pensions and rental income.
Does the calculator include UK pension rules?
Yes. It models pension access ages (default 57 unless changed) and separates pre- and post-pension income correctly.
Can it show if I can retire before accessing pensions?
Yes. The calculator checks whether your non-pension assets can fund the bridge period between early retirement and pension access.
Does it include buy-to-let income?
Yes. You can add net BTL income, choose growth assumptions and decide whether it continues throughout retirement.
How does it decide my retirement age?
It projects your assets forward year by year and identifies the earliest age at which your portfolio can sustainably support your spending.
Are the results shown in today’s money?
Yes. All figures are inflation-adjusted so you can interpret results in real terms.
Is my data stored?
No. All calculations run locally in your browser.
Can I export or print my results?
Yes. The calculator includes CSV export and a print-friendly layout for saving or sharing your projections.