Coast FIRE: How to Calculate the Amount You Need to Coast to Retirement

Coast FIRE is the point where your existing retirement savings will grow into enough to retire on by your planned retirement age — even if you stop contributing entirely and just let compounding do the work. It is a popular middle step between aggressively saving and full financial independence: you still work, but you no longer have to put a large slice of every paycheck into retirement.

Want to know your own number? Use the Coast FIRE calculator to see exactly how much you need saved today based on your age, target retirement age, and expected annual spending.

How Coast FIRE Works

Coast FIRE relies on three numbers: how much you spend per year in retirement, the safe withdrawal rate you plan to use (commonly 4%), and the number of years until retirement. The target portfolio value at retirement is annual spending ÷ withdrawal rate. Your coast number is the present value of that target, grown at an assumed investment return over the years remaining.

Example: if you plan to spend $50,000/year and use a 4% withdrawal rate, you need $1,250,000 at retirement. With 30 years to go and a 7% real return, that target is worth roughly $164,000 today. Save $164,000 by, say, age 35, and you can coast — contributions become optional.

Coast Number by Age: Quick Reference

Retirement Spending/Year	Target at 65	Coast Number at 30 (7% return)	Coast Number at 40
$40,000	$1,000,000	~$131,000	~$259,000
$50,000	$1,250,000	~$164,000	~$324,000
$60,000	$1,500,000	~$197,000	~$389,000
$80,000	$2,000,000	~$262,000	~$518,000

The Assumptions Matter

• Investment return — the calculator assumes a steady annual return (often 6–8% real). Market volatility means your actual path will be lumpy
• Inflation — use real (inflation-adjusted) returns so the numbers are in today’s dollars
• Withdrawal rate — 4% is the classic rule of thumb; more conservative retirees use 3–3.5%
• Social Security and pensions — if these cover part of your spending, your portfolio target shrinks
• Healthcare costs — retirement medical expenses can be significant; factor them into annual spending

Coast FIRE vs. Traditional FIRE vs. Lean FIRE

Approach	What It Means	Lifestyle After Reaching It
Lean FIRE	Retire on minimal spending	Retire early, live frugally
Traditional FIRE	Retire once savings cover ~4% of normal spending	Retire early, live normally
Coast FIRE	Savings will grow to your target without more contributions	Keep working, but contributions become optional
Barista FIRE	Coast plus part-time work to cover current expenses	Work part-time in a low-stress job

Steps to Find Your Coast Number

1. Estimate your retirement spending per year (start from today’s spending, adjust for paid-off mortgage)
2. Pick a withdrawal rate (4% is a common starting point)
3. Choose your target retirement age and expected annual return
4. Enter these into the Coast FIRE calculator to get your coast number
5. Compare it to your current retirement balance — the gap tells you how much more you need to save before you can coast

Is Coast FIRE Right for You?

Coast FIRE suits people who like their work but want financial flexibility, or who want to redirect savings toward other goals (a house, travel, children) once the retirement base is secured. It is riskier than full FIRE because you depend on market growth over decades — a sustained downturn near retirement can hurt. If you are close to retirement age or have a low risk tolerance, a more conservative plan may fit better.

Run your own numbers with the Coast FIRE calculator and see exactly when your savings start doing the heavy lifting.