Coast FIRE Calculator

Frequently Asked Questions

What is Coast FIRE?

Coast FIRE is the portfolio size where compound growth alone - with no further contributions - will grow your money to your retirement goal by your target retirement age. Once you reach the coast number, you only need income to cover current expenses.

How do I calculate my FIRE target?

Multiply your expected annual retirement spending by 25 for a 30-year retirement (4% withdrawal rate) or by 30-33 for an early retirement of 40+ years. Your coast number is then that target discounted back to today at your expected real return.

What return rate should I use?

A real return (after inflation) of 5-6% is a commonly used planning range for a diversified stock-heavy portfolio. Using the real return lets you express your spending target in today's dollars.

Does hitting Coast FIRE mean I can stop working?

Not necessarily. Coast FIRE means you can stop contributing new money to retirement accounts, but you still need income to cover daily living expenses until you actually retire. Many people use it as permission to downshift careers rather than stop entirely.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

Coast FIRE is the point at which your invested portfolio is large enough that it will grow on its own to your target retirement number, assuming you never contribute another dollar. The calculator works backward from your retirement goal: it asks for your FIRE target (the portfolio you need in retirement), your expected annual return, and the years until retirement, then solves for the present value of that goal.

The formula is: Coast Number = FIRE Target ÷ (1 + r)ⁿ. Once your portfolio equals or exceeds this coast number, you have technically "coasted" to retirement - every additional dollar you invest just accelerates the timeline. Many people use Coast FIRE as a milestone to give themselves permission to downshift to a less demanding job or reduce contribution pressure while maintaining the retirement trajectory.

Coast FIRE vs. Lean FIRE vs. Fat FIRE

The FIRE movement uses several related terms that share the same math but differ in the target spending level and lifestyle:

Lean FIRE: Retiring on a minimal budget - often below $40,000/year. Requires a smaller portfolio but demands significant lifestyle constraints, especially for healthcare costs before Medicare age.

FIRE / Regular FIRE: Targeting spending that matches current lifestyle, typically the portfolio size implied by your annual expenses divided by 0.04 (the 4% rule).

Fat FIRE: A large portfolio supporting $100,000+ in annual spending with extra margin, often chosen by high earners who want a comfortable safety buffer.

Coast FIRE: Not a specific spending target - rather, the point where the portfolio is large enough to reach any target without additional contributions.

Barista FIRE: Working part-time to cover current expenses while the portfolio coasts, often used to access employer healthcare benefits.

The 4% Rule and Your FIRE Target

The 4% rule, derived from the Trinity Study, states that you can withdraw 4% of your portfolio in year one of retirement and adjust for inflation each year, with a high probability of the portfolio lasting 30 years. If you plan for a 30-year retirement, multiply your expected annual spending by 25 to find your portfolio target. For a 40-year retirement (retiring early), many planners use a 3-3.5% withdrawal rate and a 28-33x multiplier to add safety margin.

Coast FIRE planning should use the same FIRE target you would use for full retirement - it is just asking a different question: how much do you need today so that growth gets you to that target without more contributions?

Return Assumptions and Inflation

If you use a nominal return (before inflation), your FIRE target should also be in nominal dollars (today's spending multiplied by an inflation factor to reflect prices at retirement). If you use a real return (after subtracting inflation), your FIRE target should be in today's dollars.

The safest approach for planning purposes: use a real return of 5-6% (nominal 7-8% minus 2-3% inflation) and express your FIRE target in today's spending. This keeps the math intuitive - your spending target is the number you live with today, not a future inflated figure.

Historically, a diversified stock-heavy portfolio has returned about 7% after inflation over very long periods. Using 5-6% real builds in a buffer for below-average sequences of returns.

Tips and Caveats

Coast does not mean stop entirely: Once you hit your coast number, you still need to cover living expenses. Most people continue working, just without the pressure to maximize retirement contributions.

Healthcare before 65 is a significant cost: Factor in insurance premiums before Medicare eligibility when calculating how much you need to earn in a Coast phase.

Market risk does not disappear: A 40% market drop the year after you hit your coast number could push the coast number out by several years. Running scenarios with 4-5% real returns adds resilience.

Coast and Roth conversions: A Coast phase with lower income can be ideal for Roth conversions - filling lower tax brackets with traditional IRA money while earned income is reduced.

Tax laws change frequently. Verify current limits at IRS.gov and consult a qualified financial advisor before making retirement decisions.

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