How to FIRE your boss

Waking up with no alarm clock.

Doing your hobbies full-time.

Keeping a job you love but without worrying about money. Exploring interests other than the already specialised 9-5 profession.

Travelling the world or connecting deeply with the local community. Doing the digital nomad thing.

Pick your desired life, that’s what money can do for you! It’s time you FIRE your boss!

The FIRE movement has come a long way. Wikipedia defines it as:

Those seeking to attain FIRE intentionally maximize their savings rate by finding ways to increase income and/or decrease expenses. The objective is to accumulate assets until the resulting passive income provides enough money for living expenses throughout one's retirement years.

Previous generations could only dream of this lifestyle.

Did you know that pensions are a thing of the 20th century? The Old Age Pensions Act was first introduced in 1908 here in the UK. For most of humanity (and even the first half of the century), most people were either just not reaching pension age or had to work until the end.

life expectancy in the UK

Obviously, the ability to make work optional in your 30s or 40s is a great luxury. It’s possible thanks to the investment income that things like buy-to-let properties or stocks can provide.

FIRE is something many of us want to reach. But is financial independence possible? And should you really pursue it?

This is a 2-part post. In the first part, I describe the maths behind financial independence and the reasons behind it. I want to analyse what it takes to get there. Part 2 will be about the dangers of early retirement – what can go wrong and how to protect ourselves.

To begin with, let’s have a look at the math. First, I want to highlight what numbers can tell us (and what they cannot). We also have many examples from people who’ve FIRE’d after such a long bull market.

How much do I need to retire early in the UK?

To make work optional, you need to gather enough savings and then invest them in income-producing assets. How much? Let’s call this The FI number.

How much can you withdraw from your portfolio every year without running out of money?

In other words, how much do I need to accumulate in order to ditch the alarm clock? First of all, many clever people have studied the math behind the question.

Assuming the often criticised 4% rule, an FI number of £100,000 can generate £4,000 a year for you, forever, without running out of money. You can lower it down to 3.5% (see SWR series) if you want to be safer.

Living expenses = 3.5% x Invested savings

When your annual living expenses cover more than 3.5% of your invested assets congratulations, you have achieved full financial freedom!

Remember, we cannot just dial up the risk and lower the FI number. That’s because investment returns won’t come just because we need them. We also need to protect our capital from the ups and downs that inevitably come with investing.

For example, a quick rule of thumb is to multiply your annual living expenses by 25 (4% of invested savings) or by 30 (3.3%). So if your living expenses are £2,500 a month, that’s £30,000 a year. As a result, to reach full financial freedom you need £30,000 x 30 = £900,000 in investments.

Passive income (month)Invested assets required (30x rule)
£1,250 £450,000
£1,750 £630,000
£2,500 £900,000
£5,000 £1,800,000
£7,500 £2,700,000
£10,000 £3,600,000
How much you need to fully FIRE your boss

Whether you use the passive income to FIRE your boss or for other purposes is entirely up to you.

No need to go full FIRE or even abandon your profession. For example, you can use it to go on better holidays, get nicer things or help the kids with the mortgage.

Using the same rules, a £450,000 sum can bring you £1,250 per month!

How do you gather the sum in the first place? Saving is more important than investing in the beginning:

  • At a savings rate of 10%, it takes (1-0.1)/0.1 = 9 years of work to save for 1 year of living expenses.
  • At a savings rate of 25%, it takes (1-0.25)/0.25 = 3 years of work to save for 1 year of living expenses.
  • At a savings rate of 50%, it takes (1-0.5)/0.5 = 1 year of work to save for 1 year of living expenses.
  • At a savings rate of 75%, it takes (1-0.75)/0.75 = 1/3 year = 4 months of work to save for 1 year of living expenses.

As you can see, the entire FIRE equation depends mainly on one factor: Your living expenses. That’s the trickiest part.

How confident are you that you are not going to miss your estimate? As someone who is more than halfway thereI think the FI number is really hard to pin down. The biggest challenge I see is finding the right number.

What Is the Average Cost of Living in the UK?

The average cost of living in the UK is £3,479 per month for a family of four or £1,955 for a single person (src:

Obviously, this is just that, an average. A family of four living in London, nice area, private schooling etc would need north of £10,000 a month. Conversely, a single person who’s a hardcore ERE fan, spending just £800 a month would need about 300k to retire early.

The earlier you start the faster the compounding machine will work in your favour. You can even retire in your 30s or 40s if you have a very high income and live like a college grad. Personally, I do have a high income but I do not live like a college grad anymore.

In any case, the main issue with FIRE math is that you have to know your living expenses to solve the equation. As you would expect, the earlier the retirement age the harder the assumptions become.

The Real Issue with FIRE maths

Predicting living expenses for the current year or even the next one is doable. But the FI Number is almost impossible to calculate long term (like 20 years), especially if you want to be on the safe side. 

It suffers from so many different assumptions.

  • Will you have kids? How many?
  • Public or private education?
  • Does your partner work? Or have you even met them? Will they be a big spender or a saver?
  • Helping the kids with housing? Will you leave an inheritance and how much?
  • Will you need to support your parents later in life?
  • Average investment returns? Future tax rates?
  • Life expectancy?

It’s not that you cannot make assumptions about these things. It’s that you take a conservative approach about all of them, then you might never reach it!

In other words, life doesn’t happen in a spreadsheet.

Ok, some people will reach their number, and some Foxy Monkey readers I know have a substantial net worth already. But not the majority.

So the aspiring FIRE seeker needs to either limit their future selves or make assumptions that make sense at the time of writing but could be wrong 20 years down the line.

Arghhhh The Number seems too high! Should I abandon the FIRE quest?

Most FIRE seekers are great problem solvers. They are also creative minds. The optional work lifestyle does not mean work is forbidden. But it means focusing on the only work that matters TO YOU.

Cutting the BS at work, the meaningless meetings, going deeper in areas you like and also learning totally different skills, like mastering cooking, hiking or machine learning. Keeping only the work that interests you even if it’s unpaid. Most likely, your post-FI activities will bring some income already. This is a big advantage to the “I don’t know what the living expenses will be like” issue.

Not everyone has to become a lifestyle YouTuber… For example, activities in a FIRE lifestyle like hobbies can actually pay you to teach beginners after a certain level.

I know what you’re thinking: This sounds like a job!! I thought I’ll be retired?

Many people will just call bullshit on the FIRE movement just because the answer to the entire question is

“Go find a job you like then!” 

But I disagree.

A job you like but depend on is a totally different proposition. Assuming you have the income from elsewhere, would you do your current job without getting paid at all?

If the answer is yes, then well done my friend. For most people, even the ones that are fairly happy in their jobs the answer would be straight no. They would perhaps do it part-time or choose to do 30-50% of the work activities.

This is why most of the successful early retirees we will meet in part 2 do some kind of work already.

To sum up, this is part of the solution actually! Having enough money to avoid being forced into doing anything you don’t like while only taking on those tasks you enjoy (even if it means changing jobs, lower pay, etc). Having the insurance that the passive income provides.

And for those of you who love their jobs and would do them for free (that’s me 8 years ago…) have you tested the limits of your freedom?

Finding the right FI number can be hard. So should I abandon the quest? No! I’d say start with a rough estimate of your desired living expenses with some room for error.

Keep learning / being active on things that interest you in FIRE. That will let you have skills that can pay you if you have miscalculated your assumptions. This should also open up other opportunities that you were too busy to explore while in a full-time job.

Also, what if you have actually overestimated what you need? Or what if your investing proves to be very successful (or lucky)? Or that you end up bringing MORE income doing work or things you love? All these paths can give the upper hand to the aspiring FIRE-seeker.

Thanks for reading. In the next part, we will visit the dangers of early retirement and how to protect ourselves. We will also peek into other people’s lives who are on the same journey.

Happy FIREing!

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    2 thoughts on “How to FIRE your boss”

    1. Thank you, Michael as always. I am glad I came across your blog last year in February before the COVID induced market crash while doing my research on limited company investment models. I have educated myself a lot and some of the books in your reading list have helped me along the way, as well as creating my own detailed current budget and spend and start investment journey. I agree with almost everything in this Part 1 blog that FI does not mean giving up work, it’s the principle of having the freedom to choose kind of work you want to do, be it paid or unpaid. One important aspect which I hope you mention in the part 2 is the role of inflation on living expenses. For example, if my current expenses in a round number are 50,000 per year and I want to be FI in 10 years, I need to take that into account that my starting number will be more than current expenses rate of 50,000 in 10 years time. Minor point however an important one in my opinion. Coming back to FI, and thinking about the permanent job before starting my Ltd company, I think the choice is usually certainty (as much as a perm salaried job can offer these days- but it’s still more certain than contract for a Ltd co director you may say) vs autonomy as a director of your Ltd co for example. What I understood in simple terms is that reaching FI where all or almost all of your expenses can be covered by your investment income eventually offers you that certainty on top autonomy which you already have as being your own boss. Studies after studies have shown that having control over your time and control over your tasks/works has the strongest link to happiness (not money or job title or anything like that but control over what you want to do, how you want to do and when you want to do).

      • Great comment, very insightful. I also see controlling your time as the ultimate form of freedom. Money is just a tool that can provide that. Being more independent and autonomous as you rightly said.

        Overall, yes there is inflation and it’s definitely something to consider, I missed that. The 3.5% safe withdrawal rate, however, assumes that you re-adjust your withdrawal number each year to add inflation without running out of money.

        Inflation is worrying but only for savings in certain assets – cash, fixed income. Depending on the asset mix, inflation can actually be your friend. With property investing, for instance, inflation is not so bad. Hard assets keep up well plus your mortgage debt is in nominal terms hence decreasing in value over time (without even paying it off).

        Stocks, which suffer from *unexpected* inflation in the short term have easily beaten inflation over 5-10 years. That’s because they are a big part of the economy, they raise their prices, they own hard assets such as factories etc. This is why sometimes I am against having a large allocation in inflation hedges (commodities) instead of inflation-beating assets.


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