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Investing Horizons · Tools

FIRE and Coast FIRE Calculator

Find your FIRE number, see the age you could reach it, and check whether what you've already saved could coast you there.

Every calculation runs right here in your browser. Nothing you type is sent anywhere, saved, or collected, and it disappears when you close the page.

This tool is for education only. It is not personalized financial, tax, or investment advice. Every projection rests on simplified assumptions, and real markets will not follow them. Talk with a licensed professional before making decisions with real money.

Choose your FIRE style

FIRE stands for Financial Independence, Retire Early: saving and investing enough that your investments can pay for your life, so work becomes optional. Pick the lifestyle you're aiming for. Coast FIRE can be added to any of them.

Retiring early on a tight, bare-bones budget. It covers the essentials with little room for extras, so it needs the smallest savings target.

Retiring early on a budget close to a typical middle-class lifestyle: comfortable, but not lavish. This is the most common target.

Retiring early with room for travel, hobbies and a generous cushion. It takes the largest nest egg of the three.

Not a spending level of its own. It checks whether what you've already saved could grow to your FIRE number by your target retirement age with no new contributions, so you'd only need to earn enough to cover today's bills.

Your inputs

Open a section to adjust it. Results update instantly.
Your timeline
years
Your age today. Every projection on this page starts from here.
years
The age you'd like work to become optional. The chart marks it on your timeline, and Coast FIRE asks whether your savings can grow to your FIRE number by this age.
Spending & withdrawal rate
$
What you expect to spend in a year once you stop working: housing, food, health care, travel, everything. Picking a FIRE style above fills this in, and you can type your own number any time. Not sure? Total up your spending with the Monthly Expense Calculator.
%
The percentage of your total savings you'd withdraw each year in retirement. It's the main lever that sets your target number: a lower rate means you need more saved, but your money can last more safely for longer. The 4% default comes from a widely cited rule of thumb suggesting a strong historical chance that a portfolio lasts thirty years or more. Some people choose a lower rate for extra safety, or a higher one if they expect a shorter retirement or have other income, like a pension or Social Security.
Savings & contributions
$
The total you've already invested toward retirement: 401(k), IRA, brokerage accounts and similar. It drives the "when will I get there" projection and the Coast FIRE check.
How you save
Pick whichever way you already think about saving. All three turn into the same yearly amount behind the scenes, and switching keeps that amount the same.
$
A set dollar amount you invest every month, such as an automatic transfer. That's 12 deposits a year.
A widely cited benchmark is saving around 15% of your gross income for retirement, sometimes counting any employer match toward that figure. People who are behind on savings, or chasing an aggressive FIRE timeline, often aim higher.
Investment growth
How returns are modeled
%
How much your investments grow in a typical year, before inflation. 7% is a common planning assumption for a mostly-stock portfolio; U.S. stocks have historically averaged a bit more than that over long periods, with big swings from one year to the next.
Inflation
Prices tend to rise, so $70,000 will buy less in 20 years than it does now. With this on, your growth rate is reduced by inflation (called a "real" return), your contributions are assumed to rise with prices so they stay the same in today's terms, and every figure is shown in today's dollars. With it off, the target isn't adjusted for rising prices, which makes the projection more optimistic.

Coast FIRE status

Whether your savings could reach your FIRE number by your target retirement age on growth alone, with no more contributions.

Your FIRE number

The total you'd need invested so that withdrawing your chosen rate each year covers your annual expenses.

$0

Your path to your FIRE number

How the math works

Your FIRE number is the savings that would let you withdraw your chosen rate each year and cover your expenses:

FIRE number = annual expenses ÷ withdrawal rate

Your coast number is today's value of that target: the amount that, left alone to grow, reaches your FIRE number exactly at your target retirement age.

Coast number = FIRE number ÷ (1 + growth rate)^(years until retirement)

The projection steps forward one day at a time, adding your contributions on their real schedule (12 or 26 deposits a year) and growing the balance at your rate. With inflation on, the growth rate becomes a real (after-inflation) return:

Real return = (1 + growth rate) ÷ (1 + inflation rate) − 1

In Monte Carlo mode, each day's return also gets a random swing sized by your volatility setting, across 150 paths. The line shows the median path, the band shows the middle 80% of paths, and each date is reported as the median with the 10th to 90th percentile range. The coast number always uses your average growth rate.

Built by Justin Wiggins. This is an educational tool, not financial advice.

This Coast FIRE calculator answers two questions: how much you need to retire early, and whether what you've already saved could get you there on its own. Pick a Lean, Regular or Fat budget, or type your own.

How this calculator works

FIRE stands for financial independence, retire early: saving and investing enough that your investments can pay your bills, so work becomes optional. Your FIRE number is that savings target, and the math is short: annual expenses ÷ withdrawal rate. At the common 4% rate, that's 25 times what you spend in a year.

Lean, Regular and Fat FIRE are the same formula at three spending levels: $40,000, $70,000 and $120,000 a year by default. At 4%, those need $1 million, $1.75 million and $3 million.

Coast FIRE is the point where your savings, left completely alone, would grow to your FIRE number by your target retirement age. The calculator works backward to your coast number: FIRE number ÷ (1 + growth rate) raised to the years until you retire. Pass it, and you'd only need to earn enough to cover today's bills.

To find your dates, the calculator steps forward one day at a time, adding deposits on their real schedule and growing the balance. With inflation on, it uses a real return (your growth rate after inflation), so every figure is in today's dollars. Randomized mode runs 150 market paths and reports the middle one.

A worked example

Say you're 30, you've invested $80,000, and you add $1,500 a month. You'd like work to be optional by 60 on a Lean FIRE budget of $40,000 a year, so your FIRE number at 4% is $1,000,000. You assume 7% growth and 3% inflation, which the calculator turns into a real return of 3.88%.

Your coast number today is $318,862, the amount that would grow to $1,000,000 by 60 with no more deposits. You're about 25% of the way there. Keep investing $18,000 a year and you'd reach Coast FIRE at about age 48.

At that pace you'd hit the full $1,000,000 at about age 55. Run the same saver through Regular FIRE and that date slides to about 66, and Fat FIRE pushes it to about 78. (These figures are illustrative, run through this calculator for a made-up saver, in today's dollars.)

Methodology and sources

The 4% default traces back to research on how long retirement savings lasted in past U.S. markets, starting with financial planner William Bengen's 1994 study and the 1998 Trinity study. Both looked at retirements of about 30 years.

The model leaves out taxes, fees and Social Security, and it grows your savings at one steady rate unless you switch to randomized markets. The 3% inflation default is close to the long-run U.S. average measured by the Consumer Price Index.

Last updated: October 2026

Frequently asked questions

What is a FIRE number?

It's the amount you'd need invested to live off your investments indefinitely. The quick version is your yearly expenses divided by a safe withdrawal rate. At 4%, that works out to 25 times your annual spending.

What's the difference between Lean, Regular and Fat FIRE?

The same idea at three spending levels: Lean is frugal, Fat is comfortable, and Regular sits in between. The defaults here are starting points, so use your own spending if you know it.

What is Coast FIRE?

You've reached Coast FIRE once your savings, left alone, would grow to your full FIRE number by the age you want to retire. From then on you only need to earn enough to cover today's bills.

How do I calculate my Coast FIRE number?

Divide your FIRE number by (1 + your expected growth rate) raised to the number of years until you retire. A $1,000,000 target, 30 years away, at a 3.88% real return works out to $318,862. If your savings are at or above that, you've reached Coast FIRE.

Is the 4% rule safe for early retirement?

It's a reasonable starting point, not a guarantee. The research behind it tested 30-year retirements, and retiring at 40 could mean 50 years of withdrawals. Many early retirees plan with 3.25% to 3.5%, which raises the target but gives the money more room.

Related tools

Monthly Expense CalculatorTotal your spending to get a real annual expense figure. Investment SimulatorTest withdrawals in randomized markets once you get there. Social Security Break-Even CalculatorCompare claiming at 62, 67 and 70 and find the age waiting pays off.

Related reading: What Investing Actually Is, and Why Anyone Bothers and Am I Ready to Retire?