What Coast FIRE means
FIRE stands for Financial Independence, Retire Early. The full FIRE number is the portfolio that can cover your yearly spending indefinitely, often set at 25 times spending (the 4% rule). Coast FIRE is an earlier milestone: the amount that, invested today and left alone, will grow into your full FIRE number by your planned retirement age.
Once you reach it, you no longer need to save for retirement. You only need to earn enough to cover your current expenses, which can mean switching to part-time work, a lower-paid job you enjoy, or a career break.
The calculation
- FIRE number = yearly retirement spending ÷ withdrawal rate
- Coast FIRE number = FIRE number ÷ (1 + real return)^(years to retirement)
The calculator also projects your current savings to retirement with no new contributions, and the age at which they would reach the FIRE number on their own.
Worked example
A 35-year-old plans to retire at 65, expects to spend $60,000 a year in today’s money, uses a 4% withdrawal rate and assumes a 5% real return. They have $250,000 invested:
| Result | Value |
|---|---|
| FIRE number at retirement | $1,500,000 |
| Coast FIRE number today | $347,066 |
| Savings minus Coast FIRE | −$97,066 |
| Savings at 65 with no new contributions | $1,080,486 |
| Age when savings alone reach $1.5 million | 71.7 |
They are about $97,000 short of Coast FIRE. Saving a bit longer, or accepting a later retirement, would get them there.
Choosing the assumptions
- Real return: use returns after inflation, because spending is in today’s dollars. A diversified stock portfolio has historically earned about 5 to 7% a year above inflation in the US, but sequences of poor years happen. Many planners use 4 to 5%.
- Withdrawal rate: 4% comes from studies of 30-year retirements using historical US returns. For retirements longer than 30 years, 3 to 3.5% is more cautious.
- Spending: subtract expected Social Security or pension income from retirement spending; this sharply reduces the FIRE number.
- Taxes and fees: withdrawals from tax-deferred accounts are taxed, and fund fees reduce returns.
Risks
Coast FIRE relies on decades of compounding. A severe market drop early on, higher inflation or lower returns can leave the portfolio short. Many people keep contributing a little after reaching Coast FIRE as a buffer, and recheck the numbers every year.
This calculator gives estimates for education and planning. It is not investment, tax or legal advice; for decisions about your own situation, talk to a qualified financial professional.