Financial Independence: Paths, Numbers, and Trade-offs

FI isn't about never working again. It's about changing "have to" into "want to." Most people who achieve FI keep working. The difference is they choose projects they care about, with people they respect, on schedules that suit them. The goal isn't to escape work. It's to escape needing work.

Whether you're pursuing FIRE, exploring concepts like CoastFI, or just want more options in life, understanding the path to financial independence starts with knowing the numbers.

What is Financial Independence?

Financial Independence (FI) means having enough assets to live without working for money. The maths is simple:

FI Number = Annual Expenses x 25

This is based on the 4% safe withdrawal rate. If you can live on 4% of your investments annually, you're financially independent.

FI Variations for Every Goal

Start by answering three questions honestly:

1. What's your minimum acceptable lifestyle cost? (LeanFI)
2. What's your comfortable lifestyle cost? (Standard FI)
3. What's your dream lifestyle cost? (FatFI)

Each answer gives you a different FI target, and a different number of years to get there. There's no wrong answer.

LeanFI

Cover just the essentials. Works well if you value time over luxury.

• Calculate: Essential expenses only x 25
• Example: £20,000/year expenses = £500,000 FI number

Standard FI

Maintain your current comfortable lifestyle without working.

• Calculate: Current annual expenses x 25
• Example: £40,000/year expenses = £1,000,000 FI number

FatFI

Financial independence with a luxurious lifestyle.

• Calculate: Dream lifestyle expenses x 25
• Example: £100,000/year expenses = £2,500,000 FI number

CoastFI

A popular FI milestone: having enough invested that compound growth alone will carry you to full FI by retirement age, without adding more. Once you reach CoastFI, the theory says you can stop aggressive saving and only need to cover current expenses from that point on. It's a useful mental model for understanding how compound growth works in your favour.

How to estimate your CoastFI number:

1. Decide your target retirement age
2. Calculate your FI number (annual expenses x 25)
3. Work backwards: how much would you need invested today, growing at your expected rate, to reach that FI number by retirement age?
4. That's your estimated CoastFI number

The exact number depends on assumptions about future returns, but the exercise itself clarifies how compound growth affects your timeline.

Example estimation:

• Current age: 30
• Assumed growth rate: 7%
• FI number: £1,000,000
• FI target age: 50

If £150,000 grows at 7% for 20 years, it reaches roughly £580,000. Not enough. But reaching £250,000 by 35 could let compound growth carry you to £1M by 50.

What reaching CoastFI would mean in practice:

• You only need to cover current expenses
• No more aggressive retirement savings required
• More room to take risks: start a business, travel, change careers
• Work becomes more of a choice

Someone earning £45,000 who estimated their CoastFI number at £300,000 might, once their investments reached that level, choose to go part-time or switch to lower-paid work they find more meaningful. The maths suggests their existing investments should compound to their full FI number without further contributions.

You can track your overall progress with the FI Progress metric in Doughsense.

Calculating Your FI Number

Step 1: Know Your Real Expenses

1. Track your real expenses for at least 3 months
2. Categorise into essential vs. discretionary
3. Annual total x 25 = Your FI number
4. Consider different FI levels: LeanFI, Standard FI, and FatFI

Step 2: Know What Counts Toward FI

Include everything that counts toward FI:

• Workplace pensions (SIPP, workplace pension)
• Personal pensions (ISAs)
• Taxable investment accounts
• Real estate investments

Don't include:

• Primary residence (unless you'll sell it)
• Cars or depreciating assets
• Emergency funds (they're for emergencies)

Step 3: Set Realistic Growth Rates

Historical averages to consider:

• Stock market: 7-10% nominal
• Bonds: 3-5%
• Real estate: 3-5% appreciation + rental yield
• Mixed portfolio: 5-8%

Choose conservative estimates. Better to be pleasantly surprised than to build a plan on optimistic assumptions.

Tracking Your Progress

Review your numbers monthly. If your FI percentage increased, good. If it didn't, work out why: is it a spending issue, an income issue, or just a market dip? Spending and income you can address. Market dips are temporary; stay the course.

Key Metrics to Monitor

FI Progress

• Current investments / FI number x 100
• Doughsense calculates this automatically as the FI Progress metric
• Watch this climb monthly
• Celebrate milestones (25%, 50%, 75%)

Years to FI

• Based on current savings rate
• See how changes affect timeline
• Model different scenarios

Savings Rate

• The most important metric. Learn about all twelve metrics you should track
• Higher rate = faster FI
• Aim for 25%+ (50%+ for rapid FI)

Safe Withdrawal Amount

• Current investments x 4%
• This is your current passive income
• Watch it grow toward your expense needs

Monthly FI Check-In

1. Update investment balances
2. Review savings rate
3. Check FI percentage progress
4. Adjust if needed

Optimising Your Path

For every financial decision, consider: how many months does this add or subtract from FI? And is the life improvement worth the time cost?

A £30,000 car might add 2 years to working. A £5,000 course might subtract 3 years if it boosts income. Calculate, decide, and move on.

Increase Income

• Model salary increases
• Add side hustles
• Track ROI on skills/education

Reduce Expenses

• Find your "enough" point
• Cut what doesn't bring joy
• Model the FI timeline impact

Optimise Investments

• Maximise tax-advantaged accounts
• Reduce fees (they compound negatively)
• Maintain appropriate risk level

Scenarios to Model

"What if I save 50% instead of 30%?"

See how many years this cuts from your FI timeline.

"What if I do geographic arbitrage?"

Model earning in expensive cities while planning to retire somewhere cheaper.

"What if markets return 5% instead of 7%?"

Stress test your plan with conservative returns.

"What if I take a mini-retirement?"

See how a year off affects your long-term timeline.

Common FI Mistakes to Avoid

1. Forgetting about taxes

• Your FI number should be based on after-tax needs
• Model tax-efficient withdrawal strategies

2. Not accounting for inflation

• Use nominal growth rates and adjust your target for inflation
• Set targets in "today's money" (inflation-adjusted) for long-term goals

3. Being too aggressive

• Don't assume 12% returns
• Don't cut expenses to misery

4. Ignoring life changes

• Kids, health, interests change; your financial plan should adapt with you
• Build in flexibility

The FI Mindset Shift

Financial Independence isn't about:

• Never working again
• Living on rice and beans
• Extreme frugality forever

Frugality matters early on, but knowing when to shift from aggressive saving to using money as a tool for living well is part of the process.

It is about:

• Having choices
• Working on what matters
• Security and peace of mind
• Time freedom

Next Steps

1. Calculate your real annual expenses and multiply by 25 for your FI number
2. Set your FI number as a goal in Doughsense
3. Add up all investment accounts to see your current FI progress
4. Estimate your CoastFI number using the formula above
5. Model different scenarios to see how changes affect your timeline
6. Track monthly and adjust as your situation changes

The maths is straightforward; the value comes from running your own numbers and reviewing them regularly. A good plan adapts.