Coast FIRE is the point at which your current portfolio — with no additional contributions — will grow to your full retirement target by your chosen retirement age. Once you've hit your Coast FIRE number, you only need income to cover current expenses, not to build future wealth.

How is the Coast FIRE number calculated?

Coast FIRE Number = FIRE Number / (1 + expected real return)^years to retirement. The FIRE Number is 25× your annual spending. The expected real return defaults to your asset allocation's historical average (roughly 6.5% for 80/20 stocks/bonds).

What's the difference between Coast FIRE and regular FIRE?

Regular FIRE means you've reached your full retirement number and can stop working entirely. Coast FIRE is an earlier milestone — you've invested enough that time and compounding will do the rest. In Coast FIRE, you still work, but only to cover living expenses.

Is Coast FIRE guaranteed?

No — like all retirement projections, it depends on future market returns. This tool runs 5,000 Monte Carlo simulations using historical returns so you can see the range of outcomes, not just an optimistic average. Higher success rates are better.

Coast FIRE Calculator

Find the portfolio size you need today to retire on schedule with zero future contributions — your Coast FIRE number.

What it does

Coast FIRE number

Instantly computed: the portfolio amount needed today to retire on schedule with zero future contributions.

Monte Carlo validation

5,000 simulations confirm whether your plan survives market downturns, not just average conditions.

Fan chart visualization

See your full projection from today to life expectancy — including the "coast" period when contributions stop.

How to use Coast FIRE Calculator

1
Enter your current age and retirement target
The longer your investment runway, the smaller your Coast FIRE number thanks to compounding.
2
Input your current portfolio value
Enter what you have invested today across all accounts (401k, Roth IRA, taxable brokerage).
3
Set your retirement spending target
Enter your expected monthly spending in retirement in today's dollars.
4
Check the Coast FIRE number
The results panel shows your Coast FIRE number — the amount you need invested right now to stop contributing and still retire on schedule.

When to use this

Have I already hit Coast FIRE?

Enter your current portfolio — if it exceeds the Coast FIRE number in the results, you're already coasting.

How many years until Coast FIRE?

Adjust your retirement age or portfolio size to find when the Coast number becomes achievable.

Technical details

Coast FIRE formula	FIRE Number / (1 + real return)^years, where FIRE Number = 25 × annual spending
Real return used	Allocation-weighted historical mean: 6.9% stocks × stockPct + 1.8% bonds × (1 − stockPct) − expense ratio
Monte Carlo	5,000 paths, block bootstrap from Shiller 1928–2024 data, all running browser-side

Frequently Asked Questions

What is Coast FIRE?: Coast FIRE is the point at which your current portfolio — with no additional contributions — will grow to your full retirement target by your chosen retirement age. Once you've hit your Coast FIRE number, you only need income to cover current expenses, not to build future wealth.
How is the Coast FIRE number calculated?: Coast FIRE Number = FIRE Number / (1 + expected real return)^years to retirement. The FIRE Number is 25× your annual spending. The expected real return defaults to your asset allocation's historical average (roughly 6.5% for 80/20 stocks/bonds).
What's the difference between Coast FIRE and regular FIRE?: Regular FIRE means you've reached your full retirement number and can stop working entirely. Coast FIRE is an earlier milestone — you've invested enough that time and compounding will do the rest. In Coast FIRE, you still work, but only to cover living expenses.
Is Coast FIRE guaranteed?: No — like all retirement projections, it depends on future market returns. This tool runs 5,000 Monte Carlo simulations using historical returns so you can see the range of outcomes, not just an optimistic average. Higher success rates are better.

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