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FIRE and Coast FIRE calculator

Find the portfolio you need to retire early, and the point where you can stop saving and let compounding finish the job.

Currency:
FIRE Number
$1,000,000
At 4% SWR ($40,000/yr)
Projected FIRE Age
Age 45.1
15.1 years from now
Coast FIRE Balance Today
$564,679
Required at age 30 for age 45
Coast FIRE Status
In Progress
$514,679 gap (age 45.1)
Savings Rate
50.0%
$45,000/yr invested

System Inputs

Adjust variables in real time. Calculations update instantly.

$50,000
$40,000
Auto-suggested
Real return = 3.88% (Fisher adjusted)Test failure rate in SWR Simulator

Real Portfolio Trajectory

Simulated in constant purchasing power (real terms) until age 100.

Real Portfolio Coast Path
Loading interactive projection...
Coast FIRE Milestone: Age 45.1
Full FIRE Milestone: Age 45.1
What moves the result most: Increasing your savings rate by +10 percentage points brings FIRE 1.9 years earlier. Trimming retirement expenses by -10% brings FIRE 1.3 years earlier.

Sensitivity Matrix: Return Rate × Savings Rate

Examines how volatile market returns and lifestyle savings rate changes shift your projected FIRE age. The base case is highlighted with an emerald border.

Nominal ReturnCurrent Rate (50%)+5% Rate (55%)+10% Rate (60%)+20% Rate (70%)
5% Return
Age 47.4
Age 46.1
Age 45
Age 43.1
6% Return
Age 46.2
Age 45
Age 44
Age 42.3
7% Return
Age 45.1Base
Age 44.1
Age 43.2
Age 41.7
8% Return
Age 44.2
Age 43.3
Age 42.4
Age 41.1

Lifestyle Tiers: Lean vs Regular vs Fat FIRE

Compare required portfolios across different retirement living standards.

Lean FIRE70% budget
$700,000
Annual Expenses: $28,000
Monthly Budget: $2,333
FIRE Age: Age 41.2
Regular FIRE100% budget
$1,000,000
Annual Expenses: $40,000
Monthly Budget: $3,333
FIRE Age: Age 45.1
Fat FIRE150% budget
$1,500,000
Annual Expenses: $60,000
Monthly Budget: $5,000
FIRE Age: Age 50.5

Disclaimer: Educational tool only, not financial advice. Results are projections based on your assumptions. Real returns vary, and past performance does not predict future results. The 4% rule is a historical guideline, not a guarantee.

How this is calculated

Transparent, deterministic formulas evaluated client-side with zero hidden assumptions.

1. Real Rate of Return (Fisher Equation)

r_real = (1 + r_nominal) / (1 + inflation) - 1

Compounding models must operate in constant purchasing power to reflect genuine future living costs without inflating target numbers arbitrarily.

2. Baseline FIRE Number

FIRE Number = Annual Retirement Expenses / SWR

Based on the empirical safe withdrawal rate literature (Bengen 1994, Trinity 1998). A 4% rate implies a 25× annual expense multiplier.

3. Coast FIRE Number Formula

Coast Number = FIRE Number / (1 + r_real)^(Target Age - Current Age)

The discounted present value of the terminal FIRE goal compounded strictly by market returns without interim additions.

4. Monthly Recurrence State Transition

S_{t+1} = S_t * (1 + r_monthly) + Monthly Contribution

Iterated discrete monthly steps evaluating portfolio growth, milestone thresholds, and optional annual contribution escalation.

Model Assumptions & Boundaries

  • Constant returns & inflation: Projections assume smooth, uniform annual returns. Sequence-of-returns volatility is not modeled.
  • Taxes and fees: All figures represent after-tax investable surplus and low-cost index investing assumptions.
  • Withdrawal initiation: Withdrawals begin at the specified Safe Withdrawal Rate of the accumulated balance at retirement.

Frequently Asked Questions

Common questions about financial independence math, Coast FIRE mechanics, and safe withdrawal rates.

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