FIRE Calculator United Kingdom

FIRE, short for financial independence, retire early, means building enough invested wealth for its returns to cover your living costs, so you no longer need to work for money. This calculator works out your FIRE number, the pot you are aiming for, and how many years of saving and investing it will take to get there.

Your FIRE number and the 4% rule

The best-known rule of thumb is the 4% rule: withdraw 4% of your pot in the first year, increase the amount with inflation after that, and history suggests a diversified portfolio should last around 30 years. Four per cent is one twenty-fifth, so the rule means you need 25 times your annual expenses. Spend £40,000 a year and your FIRE number is £1,000,000. Some people prefer a more cautious 3% (about 33 times expenses) for a longer or earlier retirement, and others use 5%. You can choose the rate, and it changes the target a lot.

How long it takes

Three things decide how long it takes: what you already have, what you add each year and the return your investments earn. The calculator grows your pot year by year at your assumed return, adds your annual saving and stops when the pot reaches the target. It reports the years and, if you enter your age, the age at which you would get there. Because growth compounds, the later years do most of the work, which is why starting early and keeping costs low matter so much.

Savings rate is the real lever

For most people, how much of their income they save matters more than the return they earn. A higher savings rate grows the pot faster and means lower spending, which shrinks the FIRE number. Cutting annual spending from £40,000 to £32,000 reduces the target by £200,000 at a 4% withdrawal rate and frees more money to invest. Test what an extra few thousand pounds a year of saving, or a leaner retirement budget, does to your date.

UK wrappers that speed up FIRE

Tax wrappers make the journey faster. A Stocks and Shares ISA lets investments grow and be withdrawn tax-free, which suits the years before you can access a pension. A pension adds tax relief at your marginal rate on the way in, but is locked until the minimum pension age, 55 now and 57 from April 2028. Many UK FIRE savers build an ISA to bridge the years until their pension and State Pension start. This calculator treats the pot as one number.

A worked example

You have £50,000 invested, save £20,000 a year, expect a 5% return and want to cover £40,000 of annual spending at a 4% withdrawal rate. Your FIRE number is £1,000,000, and you would reach it in 24 years: from age 35, at about 59. You would have paid in £480,000 yourself, with the rest from your starting pot and growth. Save more, spend less or assume a slightly higher return, and the date comes forward by years.

How to use the calculator

Enter your current savings, how much you save each year, your expected annual spending in retirement and an assumed return. Use the advanced options to set a different withdrawal rate and your current age. The result shows your FIRE number, the years to reach it, your age at that point, the projected pot and how much of it comes from your own contributions.

Assumptions and limitations

This is a projection for planning, not a guarantee. It assumes a constant annual return and a constant yearly saving, while real returns are volatile and a poor run early in retirement can matter as much as the average. It works in today’s money and does not model inflation, tax on withdrawals, the State Pension starting later and reducing the pot you need, or the different access and tax rules for ISAs and pensions. The 4% rule is a guideline drawn largely from historical US data, not a promise. Revisit the result regularly as your circumstances change.

About This Tool: FIRE Calculator UK

FIRE calculator UK: use this tool to get an instant estimate based on the figures you enter. Adjust the inputs above to match your situation, or browse all our calculators to plan your next step.