Coast FIRE calculator

Free Coast FIRE calculator (also written coastfire), no signup. Find how much you need invested today for compounding alone to reach your retirement number, the age you can stop saving at your current pace, and how much Social Security or a pension shrinks the target.

What is Coast FIRE

Coast FIRE is the point where the money you already have invested will grow to your retirement number on its own. Reaching it does not mean you can stop working. It means you can stop saving for retirement, because compounding will finish the job, and your pay only has to cover the years between now and then.

The arithmetic is one compound-growth calculation run backwards. If you need $1.5 million at 65, expect a 5% real return, and you are 35, you need roughly $347,000 invested today. Its practical value is freedom: once you coast, a lower-paid job, a sabbatical or a career change is survivable rather than reckless. The answer is very sensitive to the return you assume. Over thirty years, 5% versus 7% is close to a factor of two.

The calculator

Coast FIRE number$347,066What you need invested today
You can stop saving atAge 45After 10.3 years at $25,000 a year
Retirement target$1,500,00025× annual spending
Still needed today$197,066Today's balance grows to $648,291 with no more saving

You are $197,066 short of Coast FIRE today. At 5.0% real over 30 years you would need $347,066 invested now for compounding alone to reach $1,500,000. Saving $25,000 a year, you can stop around age 45 and let the balance coast to 65.

$0$500k$1M$1.5M$2M35404550556065ageTarget at 65: $1,500,000Stop saving at 45
Save until the coast point, then let it compound. The line stops rising steeply where contributions end. One constant real return; the sequence of returns calculator shows why the order of returns still matters.
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Coast FIRE number by age

The same target, discounted to each starting age with the inputs above. Younger rows are smaller because they have more years of compounding left, not because retirement is cheaper.

Coast FIRE number by age for a $1,500,000 target at 65 (5.0% real)
Age todayYears to retirementCoast FIRE number
2540$213,069
3035$271,935
3530$347,066
4025$442,954
4520$565,334
5015$721,526
5510$920,870
605$1,175,289

A standalone version with its own inputs is the Coast FIRE by age table.

Coast FIRE with Social Security or a pension

Your portfolio only has to fund the spending that other income does not cover. If you plan to spend $60,000 a year and expect $20,000 from Social Security, the portfolio target at a 4% withdrawal rate falls from $1,500,000 to $1,000,000. At 35 with a 5% real return, the Coast FIRE number falls with it, from about $347,000 to about $231,000. Enter the benefit in today's dollars; your estimate is on your my Social Security account. If benefits start several years after you retire, the portfolio has to cover the full spend until then, so treat the result as optimistic by that gap.

Coast FIRE for couples

Run the household as one plan. Add both partners' invested balances, use your combined retirement spending, and enter the combined Social Security or pension income. Use the age of the partner who will stop working first, because that is when withdrawals start. If one partner keeps saving after the other coasts, enter the saving that continues until the coast point.

How it works

Spending minus other income, divided by the withdrawal rate, is the retirement target (4% is 25 times). That target is discounted back to today at the real return. With the figures above, $1,500,000 over 30 years at 5.0% is $347,066 today. The stop-saving age solves for the first point at which your balance, left alone from then on, still grows to the target by 65.

Coast FIRE is one of several milestones. The FIRE calculator keeps saving until the whole number is reached, and the Barista FIRE calculator sizes a plan where part-time pay covers part of spending.

Assumptions

One constant real return, contributions at year end, no fees, and a withdrawal rate that holds for your horizon. Social Security and pensions are treated as starting at your retirement age and rising with inflation. Markets do not deliver a constant return: see the sequence of returns calculator and the Monte Carlo retirement calculator. A 1% fee is a large change over decades; the fee calculator sizes it. Spending rules that flex once you are drawing are the Guyton-Klinger calculator and the Vanguard dynamic spending calculator.

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Frequently asked questions

What is Coast FIRE?
The point at which your existing invested savings, with no further contributions, would grow to your retirement target by your chosen retirement age.
What real return should I assume?
Between 4% and 6% after inflation is a common range for a diversified equity-heavy portfolio. The result is very sensitive to this number, which is why a simulation that models a range of outcomes is more informative than any single assumption.
Does reaching Coast FIRE mean I can stop working?
No. It means you can stop saving for retirement specifically. You still need income to cover current living costs until you retire.
How do I calculate my Coast FIRE number?
Work out your retirement target (annual spending divided by your withdrawal rate), then divide it by (1 + real return) raised to the number of years until retirement. $1,500,000 needed in 30 years at a 5% real return is about $347,000 today.
Does Social Security count toward Coast FIRE?
Yes. Your portfolio only has to fund the spending Social Security or a pension does not cover. $60,000 of spending with $20,000 of benefits needs a $1,000,000 portfolio at 4% instead of $1,500,000, which cuts the Coast FIRE number by a third.
How does Coast FIRE work for couples?
Treat the household as one plan: combine both invested balances, your joint retirement spending and your combined benefits, and use the age of the partner who stops working first.
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