You’ve reached Coast FIRE when your current investments, left to compound with no further contributions, will grow into your full FIRE number by your target retirement age. From that moment, your retirement is effectively already funded — you only need to earn enough to cover today’s bills, not to keep saving. It’s the milestone that turns “I have to keep grinding” into “I can ease off.”
Check where you stand with the Coast FIRE Calculator. Below, we unpack the math and what it means in practice.
The idea in one sentence
Compounding does the heavy lifting late. A dollar invested at 32 has decades to multiply; a dollar invested at 60 barely moves before you need it. Coast FIRE asks a precise question: is the money I already have enough that time alone will carry it to my number?
If yes, every additional dollar you save from here is optional — a margin of safety or a ticket to retire earlier, not a requirement.
How to calculate your Coast number
Start with your FIRE number — your annual spending times 25. Then discount it back to today using your expected real return and the number of years until retirement:
Coast number = FIRE number ÷ (1 + real return)^years to retirement
If your current portfolio is at or above that Coast number, you’re coasting. The calculator does this for you and also projects what today’s balance grows into by your target age.
Here’s how the Coast number for a $1,000,000 FIRE target shrinks the earlier you start, assuming a 6% real return:
| Current age | Years to age 65 | Coast number needed today |
|---|---|---|
| 25 | 40 | ~$97,000 |
| 32 | 33 | ~$147,000 |
| 40 | 25 | ~$233,000 |
| 50 | 15 | ~$417,000 |
| 60 | 5 | ~$747,000 |
The takeaway is stark: a 25-year-old needs under $100k invested to coast to a million by 65, while a 60-year-old needs nearly $750k. Time is the cheapest input to retirement, and it’s the one you can never buy back.
What Coast FIRE unlocks
Hitting Coast FIRE doesn’t mean you stop working — it means you stop having to save. That opens up real choices:
- Switch to lower-paying, more meaningful work. Your salary only needs to cover current expenses.
- Go part-time (Barista FIRE). Cover today’s costs and, often, health benefits, while the portfolio coasts.
- Take a career break or start a business without derailing retirement.
- Keep saving anyway to retire earlier than your original target, or to widen your safety margin.
Coast FIRE vs full FIRE
These are different milestones, and it helps to keep them straight:
| Coast FIRE | Full FIRE | |
|---|---|---|
| Portfolio funds spending today? | No | Yes |
| Need to keep contributing? | No | No |
| Need to keep earning? | Yes — to cover current expenses | No |
| Typical timeline | Reached years earlier | The final goal |
Full FIRE means your portfolio already covers your spending right now, so you can stop working entirely. Coast FIRE is the earlier, gentler milestone — the day you can take your foot off the savings pedal.
A worked example
You’re 35, want to retire at 65, and your FIRE number is $1,200,000. Expecting a 6% real return:
- Years to retirement: 30.
- Coast number = $1,200,000 ÷ (1.06)^30 ≈ $209,000.
- If you have $230,000 invested today, you’re past your Coast number — congratulations, you’re coasting. Your $230,000 should grow to about $1,320,000 by 65 with no new contributions.
- If you have $150,000, you have a gap of roughly $59,000 to close before you can coast.
The Coast FIRE Calculator shows both the target and the projected future value so you can see exactly where you land.
The assumptions that matter
Coast FIRE rests on two fragile assumptions: a steady real return and a fixed retirement date. Reality is bumpier.
- Returns vary. A 6% average can hide a brutal early stretch. Because you’re relying on compounding, a weak first decade can leave you short — understand how compound interest builds wealth and why the early years carry the most uncertainty.
- Life changes. A bigger retirement lifestyle raises your FIRE number and your Coast number with it.
- You still need health coverage and an emergency fund while coasting.
Because of this, many people aim to over-shoot their Coast number, or keep contributing for a few more years to build a buffer. Hitting Coast FIRE is permission to relax, not a guarantee.
Make the most of the years before you coast
Until you cross the line, the usual accelerators apply: keep your savings rate high, capture your full 401(k) employer match, use 2026’s higher contribution limits, and pick tax-efficient accounts (see Roth vs Traditional: Which Wins?). The sooner you reach your Coast number, the longer compounding works in your favor.
As always, these are estimates, not financial advice. Confirm contribution limits with the IRS and run your own numbers with a qualified professional. Coast FIRE is one of the most motivating numbers in personal finance — it’s the day you find out your future self is already taken care of.