Use the Financial Independence planner to compare current assets, contributions, target age, withdrawal assumptions and plan longevity.
Coast FIRE means having enough invested today that, if the portfolio grows as assumed and you make no further retirement contributions, it could reach the retirement target by the chosen retirement age. You may still need earned income to cover current living costs; the concept removes the modeled need for additional retirement saving, not the need to pay today’s bills.
Coast FIRE is not the same as being financially independent today.
At full financial independence, the portfolio is intended to support current or near-term living expenses without relying on continued work income. At Coast FIRE, the retirement component may be on track under the model, but current expenses still need to be funded by work or another source.
The concept is a present-value question
That equation is only as good as its assumptions. The future target, growth rate, inflation basis, taxes, fees and time horizon must be internally consistent.
Why the number can move a lot
- A lower return assumption raises the amount needed today.
- A shorter time horizon raises the amount needed today.
- A higher future spending target raises the Coast amount.
- If future spending rises with lifestyle inflation, the target can move even after you thought you had reached the milestone.
Coast FIRE can be useful as a flexibility milestone
The concept can help answer a different question from traditional FIRE: Instead of "Can I stop working?", it asks "Could I reduce or redirect future retirement contributions if the current portfolio stays on track?" That may create room for other goals, career changes or reduced hours, but it does not remove the need to fund present-day living costs.
Do not confuse a modelled milestone with a guarantee
Real investment returns are not constant. A Coast calculation should be revisited after large market changes, changes in spending, a different target age or a major change in contributions. Taxes and fees can also reduce growth.
The core calculation discounts the future retirement target back to today
Future retirement target ÷ (1 + assumed growth rate)^years remaining| Years until retirement | 4% real growth | 5% real growth | 6% real growth |
|---|---|---|---|
| 15 years | $1.67 million | $1.44 million | $1.25 million |
| 20 years | $1.37 million | $1.13 million | $935,400 |
| 25 years | $1.13 million | $885,900 | $699,000 |
| 30 years | $925,000 | $694,100 | $522,300 |
This illustration assumes a $3 million target expressed in today’s purchasing power and therefore uses real growth rates. If the target is a future nominal amount, nominal return assumptions must be used instead. Mixing the two is one of the most common Coast FI errors.
Coast FI is extremely sensitive to time and return assumptions
The earlier the coast point, the more years the existing portfolio has to compound—and the more years there are for actual returns to deviate from the assumption. A person with 30 years remaining can have a much lower Coast amount than someone with 15 years, but also more model uncertainty.
The retirement target still has to be credible
A Coast calculation can look precise while resting on a weak retirement target. Before calculating the coast amount, model retirement spending, non-portfolio income, retirement duration, inflation and withdrawal strategy. If those assumptions change, the Coast point changes.
Coasting is not the same as de-risking
Reaching the mathematical Coast amount does not mean the portfolio can be put entirely in cash. The growth assumption depends on an asset allocation that carries risk. Conversely, keeping an aggressive portfolio solely to preserve an optimistic growth rate may be inconsistent with the investor’s capacity for loss.
Why continuing some contributions can still be valuable
- It creates a buffer if returns disappoint.
- It can fund a higher future lifestyle or earlier retirement.
- It reduces dependence on a single return assumption.
- It can compensate for periods of unemployment or contribution pauses later.
- It may let the portfolio gradually de-risk while keeping the target intact.
Stress-test the coast decision
- Reduce the expected real return by 1–2 percentage points.
- Increase the retirement target for higher spending or a longer horizon.
- Model an immediate market decline before the coast period begins.
- Check whether taxes/fees are reflected in the growth assumption.
- Recalculate every year rather than treating Coast FI as a permanent status.
The Coast amount is a present value of a future liability
Thinking of it this way exposes the two biggest assumptions: The future retirement target and the discount/growth rate. If either is wrong, the Coast amount changes. A high real growth rate discounts the target aggressively and makes the required amount look deceptively small.
Continuing contributions buys insurance against model error
After reaching the projected Coast amount, even a modest ongoing contribution can create substantial margin over 20–30 years. That margin can absorb lower returns, higher retirement spending or a desire to retire earlier. “Coast” is therefore an option, not an instruction to set contributions to zero.
A career change is often the real objective
Many people use Coast FI to justify moving from high-pay/high-stress work to lower-pay work that covers current expenses. Model the new cash flow carefully: If the new job does not fully cover living costs, portfolio withdrawals begin early and the strategy is no longer pure Coast FI.
Worked example: A Coast FIRE number is the present value of a future target
Assume a future retirement target of 30,000,000 in today’s purchasing-power terms, with 20 years until the target age. If the illustration uses a real return, the target can stay in today’s money because inflation is already removed from the return assumption.
| Assumed real return | Illustrative amount needed today | Interpretation |
|---|---|---|
| 3% | 16,610,273 | Lower assumed growth means more must already be invested |
| 4% | 13,691,608 | Middle illustration |
| 5% | 11,306,684 | Higher assumed growth reduces the calculated coast threshold |
The calculation is highly sensitive to the return, time horizon and retirement target. Reaching an illustrated coast threshold does not automatically mean someone can stop all saving, stop working, ignore emergency reserves or stop funding nearer goals.
Checklist: Treat Coast FIRE as a milestone, not permission to switch off the plan
- Define the future retirement target before calculating the coast amount.
- Use a return assumption that matches the money basis and risk you are actually willing to take.
- Check how many years remain until the target age.
- Keep near-term spending, emergency reserves and other goals separate from the retirement portfolio.
- Stress-test a lower return and a higher retirement target.
- Review the result after major changes in spending, asset allocation, income or retirement timing.
For the broader target, see the financial-independence number guide. For the modeled path from current assets and contributions, see When could you reach financial independence?.
Frequently asked questions
Does Coast FI mean I can stop working?
No. It means the retirement portfolio may no longer require additional contributions under the assumptions. Current living expenses still need to be funded unless you have other resources.
Should I use nominal or real returns?
Use real returns if the retirement target is stated in today’s purchasing power; use nominal returns if the target is a future nominal amount. Keep the basis consistent.
What happens if markets fall after I reach Coast FI?
Your Coast status can disappear. Recalculate from the new balance and remaining years rather than assuming the earlier label is permanent.
Is Coast FI a guaranteed milestone?
No. It is a projection based on a future return path and retirement target. Treat it as a planning checkpoint and stress-test it.
Sources and how this guide was prepared
This Carrowmont guide was drafted with AI assistance, then structured and checked against the cited external sources and Carrowmont calculation conventions. Worked examples are illustrative, use simplified assumptions, and are not forecasts or individualized recommendations.