What is the FIRE number?

The portfolio size that lets you live off withdrawals indefinitely — annual expenses ÷ safe withdrawal rate. At a 4% rate that is 25× your annual expenses.

What is the 4% rule's role here?

The 4% safe withdrawal rate is the default assumption for how much you can sustainably draw from the portfolio each year. Lower it (e.g., 3.5%) for a more conservative target.

Coast FIRE is the amount that, with no further contributions, grows to your full FIRE number by a target age. Once you hit it you only need to cover current expenses.

Lean FIRE targets a minimal-spending lifestyle (we model 70% of expenses); Fat FIRE targets a comfortable one (150% of expenses). Each changes the FIRE number proportionally.

Is reaching FIRE guaranteed?

No. Projections use a fixed average return; markets vary. Maintain flexibility and a margin of safety.

FIRE Calculator

Find your FIRE number and the age you could reach financial independence — and compare Lean, Coast, and Fat FIRE.

Your path to FIRE

Current age Invested assets

Annual expenses

Annual savings (invested)

Expected return

Withdrawal rate

Your FIRE number

Lean FIRE

FIRE

Fat FIRE

Coast FIRE (to age )

You need invested today so it grows to your FIRE number with no further saving. You've reached Coast FIRE.

How to Use

1
Enter age & assets. Add your current age and current invested assets.
2
Add spending & saving. Enter your annual expenses and how much you invest per year.
3
Set assumptions. Adjust expected return and your safe withdrawal rate (4% default).
4
See your FIRE plan. See your FIRE number, FIRE age, and Lean/Coast/Fat variants.

Calculation Method

Your FIRE number is annual expenses divided by the safe withdrawal rate (25× expenses at 4%):

FIRE number = annual_expenses ÷ (SWR%)
Coast number = FIRE number ÷ (1 + r)^{(target_age − age)}

We then grow your assets each year by the expected return plus annual savings until they reach the FIRE number, giving your FIRE age. Lean FIRE uses 70% of expenses; Fat FIRE uses 150%.

Examples

Example. $50,000 annual expenses at a 4% withdrawal rate gives a FIRE number of $1,250,000. Starting at 35 with $100,000 invested and saving $25,000/year at 7%, that is reached in roughly the early 50s.

Frequently Asked Questions

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Disclaimer: Calculations are projections based on the assumptions you provide and are for informational purposes only. They are not financial, tax, or investment advice. Investment returns are not guaranteed. Consult a Certified Financial Planner (CFP) before making retirement decisions.

Data source: 4% safe-withdrawal rule (25× annual expenses). Coast FIRE assumes growth to a target age with no further saving.