What is Coast FIRE and how is it different from regular FIRE?

Coast FIRE is the point where your invested savings, left alone, will grow to your full FIRE number by retirement without any additional contributions. Regular FIRE means you have already accumulated enough to retire now and live off withdrawals. Coast FIRE is a milestone along the way — once you hit it, you only need to cover living expenses from your income, not save for retirement.

What is a FIRE number?

Your FIRE number is the total portfolio balance you need at retirement to safely fund all your living expenses indefinitely. It is calculated using the Safe Withdrawal Rate (SWR): FIRE Number = Annual Expenses ÷ SWR. At the most common 4% SWR, $60,000/year in expenses requires a FIRE number of $1,500,000. The 4% rule is based on historical data showing that a balanced portfolio can sustain that withdrawal rate for 30+ years.

What is the 4% Safe Withdrawal Rate?

The 4% rule comes from the Trinity Study (1998), which analyzed historical stock and bond returns and found that a 4% annual withdrawal rate had a very high success rate over 30-year retirement periods. Retirees who plan for a longer retirement (40+ years) often use 3%–3.5% to be more conservative. Adjusting the SWR in this calculator lets you model different risk tolerances.

How much do I need to save to Coast FIRE at 35?

It depends on your annual expenses and target retirement age. If you spend $60,000/year, want to retire at 65, and expect a 7% annual return, your FIRE number is $1,500,000 and your Coast FIRE number at age 35 is approximately $393,000. With $393,000 invested today at 7%, it will grow to $1,500,000 in 30 years without any additional contributions. Use this calculator to model your specific numbers.

What annual return should I use in the Coast FIRE calculator?

The most commonly used assumption for a diversified stock portfolio is 7% — the approximate inflation-adjusted historical average of the S&P 500. Use 10% if you want a nominal (pre-inflation) estimate. Conservative planners often use 6% to account for portfolio fees and potential below-average future returns. Bond-heavy portfolios typically use 3%–5%. These are historical estimates; actual returns are not guaranteed.

Can I reach Coast FIRE without stopping work?

Yes — Coast FIRE does not mean you stop working, only that you stop needing to save for retirement. Once coasted, your income only needs to cover your current living expenses. Many people in the FIRE community see Coast FIRE as a major stress-reduction milestone: you can shift to a lower-paying or more enjoyable job, reduce hours, or take career risks without worrying about retirement savings.

What if my current savings are already above the Coast FIRE number?

Congratulations — you are already coasting! That means your existing investments, compounding at your assumed return rate, will reach your full FIRE number by your target retirement age without any additional contributions. You can stop investing for retirement entirely if you wish, though many people continue saving to retire earlier or increase their retirement spending.

Coast FIRE Calculator — FIRE Number & Monthly Savings

Calculates your FIRE number, Coast FIRE number, and monthly savings needed to stop contributing and let compound growth do the rest.

How to Use This Coast FIRE Calculator

This Coast FIRE calculator shows how close you are to coasting to retirement — enter your current savings, your expected annual expenses in retirement, your current age, your target retirement age, the expected annual return on your investments, and your safe withdrawal rate. The calculator instantly returns your FIRE number, your Coast FIRE number, how much more you need to save, and the monthly contribution required to coast to retirement on schedule. Use the share button to bookmark your exact inputs.

For projecting the raw growth of any investment, pair this with our future value calculator to model different return scenarios.

What Is the FIRE Number Formula?

Your FIRE number is the retirement portfolio balance that can sustainably fund your annual expenses forever (or for a very long retirement). It is calculated as:

FIRE Number = Annual Expenses ÷ Safe Withdrawal Rate

At the standard 4% SWR, every $40,000/year of expenses requires $1,000,000 in savings. At $60,000/year: $60,000 ÷ 0.04 = $1,500,000. Lowering the SWR to 3.5% raises the target to $1,714,286 — useful for planning a 40+ year retirement.

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How the Coast FIRE Number Is Calculated

The Coast FIRE number is the present value of your FIRE number — the amount you need invested today so it grows to your FIRE number by retirement, with no additional contributions. The formula uses the standard present value equation:

Coast FIRE Number = FIRE Number ÷ (1 + Annual Return)^{Years to Retirement}

For example: FIRE number $1,500,000, 30 years to retirement, 7% return: $1,500,000 ÷ (1.07)³⁰ = $197,290. That is all you need invested today at 35 to reach $1.5M by 65 without saving another dollar.

Coast FIRE vs. Lean FIRE vs. Fat FIRE

The FIRE community uses several benchmarks, each with a different level of spending:

Lean FIRE — retire on $25,000–$40,000/year. FIRE number: $625K–$1M. Requires significant frugality.
Regular FIRE — retire on $40,000–$60,000/year. FIRE number: $1M–$1.5M. The most common target.
Fat FIRE — retire on $100,000+/year. FIRE number: $2.5M+. Offers a comfortable, flexible lifestyle.
Coast FIRE — a milestone, not a final destination. You have saved enough to let compounding carry you to any of the above without more contributions.

The Safe Withdrawal Rate Explained

The safe withdrawal rate (SWR) is the percentage of your portfolio you can withdraw annually without running out of money during retirement. The 4% rule — derived from the 1994 Trinity Study — found that a 4% annual withdrawal from a 50/50 stock-bond portfolio survived all 30-year historical periods without depletion. A 3.5% SWR is more conservative for early retirees planning 40+ years. A 3% SWR is extremely conservative and covers almost all scenarios, including extended low-return environments.

Adjusting your SWR in this calculator is one of the most powerful levers: dropping from 4% to 3.5% increases your FIRE number by 14%, while increasing from 4% to 5% reduces it by 20%. For tax planning alongside retirement projections, see our IRA calculator to model Traditional vs. Roth account growth and tax savings.

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Monthly Savings Strategy After Reaching Coast FIRE

Once you hit your Coast FIRE number, you have several options:

Stop retirement contributions entirely — invest only what you need to cover current expenses
Downshift careers — take a lower-paying job, go part-time, or pursue passion projects without worrying about retirement savings
Continue saving (optional) — extra contributions bring your retirement date closer or increase your FIRE number
Build taxable investments — once IRA and 401(k) limits are covered, taxable accounts give more flexibility for early retirement before age 59½

Common Mistakes When Planning for Coast FIRE

Using nominal returns without inflation adjustment — a 10% nominal return becomes ~7% in real (purchasing-power) terms at average inflation. Use 7% for real projections, 10% for nominal.
Underestimating retirement expenses — healthcare costs typically rise in retirement. Add a buffer of 10%–20% to your current expense estimate.
Ignoring sequence-of-returns risk — a market crash early in retirement is more damaging than one mid-retirement. The SWR accounts for this, but it is why many planners use 3.5% rather than 4%.
Not updating the calculation — recalculate annually as your savings balance, expected expenses, and return assumptions change.

Financial Disclaimer

This calculator is for planning and educational purposes only. It is not financial advice. Investment returns are not guaranteed and historical performance does not predict future results. The safe withdrawal rate is a historical guideline, not a guarantee. Consult a qualified financial advisor before making retirement planning decisions.

Coast FIRE Calculator