The pot that coasts to your target with no more saving.
Coast FIRE number
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Status
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Surplus or gap
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Your breakdown
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The point where you can stop feeding the pot
Coast FIRE is a quieter cousin of full financial independence. The idea is not that you stop working, but that you have saved enough early that compound growth alone will carry your existing pot to your retirement target by the time you finish. Once you hit your Coast FIRE number you can, in theory, stop making new contributions and let the market do the rest, while your job only needs to cover today’s living costs. This calculator works out that number and tells you whether your current savings already clear it.
The maths is a present-value calculation run in reverse. Your Coast FIRE number is your target divided by one plus your expected return, raised to the power of the years left until retirement. Put plainly, it is the lump sum that, left untouched and compounding at your assumed rate, lands exactly on your target on the day you retire. The further you are from retirement, the smaller that number, because growth has more years to work.
A 35 year old aiming for €1 million at 65
Take someone aged 35 who wants a €1 million pot by 65, assuming a 5 percent annual return. That is 30 years of compounding. Discounting €1 million back 30 years at 5 percent gives a Coast FIRE number of about €231,377. That is the amount they would need invested today to coast to the target without saving another cent. With €150,000 currently saved, they are roughly €81,377 short, so they are not at Coast FIRE yet, but they are well on the way and a few more years of contributions would close the gap.
The Irish wrinkle: where is the money sitting?
Here is the judgement call that matters in Ireland specifically. Coast FIRE assumes the pot keeps compounding and is available at retirement, but the most tax-efficient place to grow money here is a pension, and pension money is locked away. Occupational and personal pension funds generally cannot be touched before 50, and often not until 60, so a Coast FIRE number that is mostly inside a pension is real but illiquid. If your plan is to stop work well before then, you need a separate bridge of accessible savings to live on until the pension unlocks, and this tool does not model that timing gap.
Why the return assumption rules everything
The other thing to treat with suspicion is the return assumption. The whole calculation is exquisitely sensitive to it, because the rate is compounded over decades. Nudging the expected return from 5 percent to 6 percent slashes the Coast FIRE number, which can flatter your progress and tempt you to stop saving too early. My steer is to use a conservative real return, after inflation, and to remember that the target should itself be expressed in today’s money so you are comparing like with like. A €1 million target in 30 years buys a good deal less than €1 million does now.
If I reach Coast FIRE, should I really stop investing?
Reaching it means you could stop new contributions and still hit the target on the central assumptions, but it does not make stopping wise. Markets disappoint, you may retire earlier than planned, or your target may rise, and any of those can pull you back below the line. Many people who hit Coast FIRE keep contributing at a reduced level to build a safety margin rather than cutting saving to zero.
How is Coast FIRE different from full FIRE?
Full FIRE is the much larger pot that lets you stop working entirely and live off withdrawals now. Coast FIRE is the smaller, earlier milestone where you only need to keep covering current expenses while existing investments grow into the full number later. Coast FIRE is reached years before full FIRE, which is why it is a popular interim goal for people in their thirties.