What is the Lean FIRE Calculator?
The Lean FIRE Calculator helps you work out how much you need to save and when you could reach financial independence in the UK with a lower annual spending target. It calculates your Lean FIRE number and estimates the age at which your savings could sustainably support that lifestyle.
How the Calculator Works?
This calculator begins by calculating your Lean FIRE number, which is your target annual spending divided by your chosen withdrawal rate.
It then models your assets year by year while you are still working. Each pot, including pension, ISA, GIA and cash, grows at your chosen real return. Monthly contributions are added, and progress towards your Lean FIRE target is tracked.
If you plan to receive the UK State Pension, DB pension income or other reliable income later in life, the calculator reduces the required portfolio size accordingly.
When your portfolio reaches the required level, the calculator identifies your Lean FIRE age. If that age is before pension access, it models a bridge period funded by cash and ISA or GIA balances until pension access age.
During retirement, withdrawals follow a tax-aware order, typically cash first, then ISA or GIA, then pension once accessible.
Step One: Set Your Lean Spending Target
Enter your desired annual retirement spending and withdrawal rate to calculate your Lean FIRE number.
Step Two: Add Pots and Contributions
Enter balances and monthly contributions for pension, ISA, GIA and cash.
Step Three: Review Timeline and Sensitivity
See your projected Lean FIRE age, percentage progress and how changes in growth or contributions affect the timeline.
Disclaimer: This calculator provides illustrative projections only and does not constitute financial advice. Investment returns, tax rules and spending needs may differ from assumptions. Always consider professional advice before making financial 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 Lean FIRE Calculator?
It is a UK-specific planning tool that calculates your Lean FIRE number and estimates when your savings could sustainably fund a lower-cost early retirement.
What is Lean FIRE?
Lean FIRE is a version of Financial Independence, Retire Early that targets a lower annual spending level, allowing retirement with a smaller portfolio.
How is the Lean FIRE number calculated?
It is calculated by dividing your target annual spending by your chosen withdrawal rate.
Does it include the State Pension?
Yes. You can include expected State Pension income and specify the start age and amount.
Can I include DB pensions or rental income?
Yes. Guaranteed or additional income reduces the amount your portfolio must provide.
What is a bridge period?
If you reach Lean FIRE before pension access age, the calculator models funding the gap using accessible assets like ISA and cash.
What is Coast FIRE shown in the insights?
Coast FIRE shows the age at which you could stop contributing and let existing investments grow to reach your Lean FIRE target.
Are figures inflation-adjusted?
Yes. All projections are in real terms to reflect purchasing power.
How sensitive is the result to growth assumptions?
Very. The calculator shows how lower or higher return assumptions can significantly change your Lean FIRE timeline.
Can I export the projections?
Yes. Year-by-year saving and drawdown tables can be exported.
Is my data stored?
Inputs are stored locally in your browser for convenience. No personal data is transmitted.