What is the Fat FIRE Calculator?
The Fat FIRE Calculator helps you calculate how much you need and when you could retire in the UK with a comfortable, lifestyle-focused retirement. It models a retirement that includes travel, hobbies and discretionary spending, rather than just covering essentials.
How the Calculator Works?
The calculator first determines your Fat FIRE number, which is the total portfolio required to support your target annual spending at your chosen withdrawal rate. It then factors in any guaranteed income, such as the State Pension or a Defined Benefit pension, which reduces the amount your investment pots must provide.
Your pension, ISA, GIA and optional cash balances grow year by year based on your chosen real return assumption. Monthly contributions are added while you are still working.
When your portfolio reaches the required level, the calculator identifies your projected Fat FIRE age. If this occurs before pension access age, it models a bridge period funded by cash, ISA and GIA balances until your pension becomes accessible.
It also calculates your Coast FIRE age, which shows when you could stop contributing and allow existing investments to compound to your Fat FIRE target by pension access age.
All calculations are shown in real terms to reflect today’s purchasing power.
Step One: Define Your Fat Lifestyle Target
Enter your desired annual retirement spending, withdrawal rate and growth assumption.
Step Two: Add Pots and Income Sources
Enter balances and contributions for pension, ISA, GIA and cash. Include State Pension, DB pension and other income if applicable.
Step Three: Review Timeline and Bridge Strategy
See your Fat FIRE age, progress percentage, shortfall if any and how ISA or GIA balances bridge the gap to pension access.
Disclaimer: This calculator provides illustrative projections only and does not constitute financial advice. Investment returns, pension rules and spending levels vary. Always consider professional advice before making 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 Fat FIRE Calculator?
It is a UK-specific planning tool that calculates the portfolio required to retire early with a comfortable, discretionary lifestyle and estimates when you could reach that goal.
What is Fat FIRE?
Fat FIRE refers to retiring early with a higher level of discretionary spending, allowing for travel, hobbies and lifestyle flexibility.
How is the Fat FIRE number calculated?
It is calculated by dividing your target annual spending by your chosen withdrawal rate, adjusted for any guaranteed income.
Does it include the State Pension?
Yes. You can toggle the State Pension on or off and set the expected start age and annual amount.
How does the bridge to pension access work?
If you reach Fat FIRE before pension access age, the calculator models using ISA, GIA and cash balances to fund spending until pensions unlock.
What is Coast FIRE in this context?
Coast FIRE shows the age at which you could stop contributing and let existing investments grow to your Fat FIRE target by pension age.
What withdrawal rate should I use?
A common default is 3.5% for a more conservative, comfort-focused retirement, but you can adjust it to reflect your risk tolerance.
Are figures inflation-adjusted?
Yes. All projections are in real terms to reflect purchasing power.
How sensitive is the result to growth assumptions?
Very. Higher or lower growth rates can significantly affect your projected Fat FIRE age.
How should I define ‘comfortable’ without guessing?
Build the budget from real categories and planned experiences. Include housing, travel, eating out, hobbies, family help, cars and healthcare, then separate the basics from luxuries. Fat FIRE is not a competition to reach the highest number. It is a plan for a more expensive lifestyle with enough room when costs or markets change.
Can spending be higher early and lower later?
Yes, and that may be the life you want. Show more travel in the active years, a steadier middle stage and the cost of help or care later. Do not assume all later spending vanishes. A spending curve can be more honest than one flat inflation-adjusted budget for life.
Should I include second homes or expensive assets in the FIRE number?
Include the purchase price, tax, maintenance, insurance and any eventual selling costs. If the asset will not produce money you can spend, keep it separate from the investment portfolio. A large net worth can still produce weak cashflow if too much of it sits in assets that cost money to own.
What is the biggest risk once the plan looks overfunded?
Lifestyle creep can keep moving the target, while too much caution can postpone freedom indefinitely. Set a lifestyle you value, test lower returns and higher costs, then decide what any surplus is for, such as gifts, charity or extra security. More money is not always better if earning it uses healthy years you wanted for something else.
Can I export the projections?
Yes. Projection tables can be downloaded for further analysis.
Is my data stored?
Inputs are stored locally in your browser for convenience. No personal data is transmitted.
Trust and education
Certified Money First Aider®
These calculators are built by a Certified Money First Aider to help you think more clearly about money and time. Money First Aid® is about practical, non-judgemental support for financial wellbeing. The calculators can certainly help you make informed decisions, but they are not regulated financial advice.
Behind Retirement Calculators
Built from the questions I was asking myself
I'm Ryan, the person behind Retirement Calculators. I started the site after selling an online business and trying to understand what our pensions, ISAs, investments and property actually meant for the way we wanted to live.
The calculators are built around those real decisions: whether you could work less, retire earlier, spend more now or use your money differently. They will not give you a perfect answer, but they can make the trade-offs much easier to see.
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