Use Coast FI as a motivating intermediate milestone
Coast FI is the point where your current portfolio, left alone, will compound to full FI by a traditional retirement age.
Key takeaways
- What it is: Coast FI is the point where your current portfolio, left alone, will compound to full FI by a traditional retirement age.
- Why it works: Coast FI reframes the accumulation journey by separating the compounding function from the savings function. Once you reach Coast FI, investment growth alone will carry the portfolio to full FI by a target age — you no longer need to save, only to cover current expenses. This milestone is typically reached much earlier than full FI and creates a genuine choice point: continue the high savings rate for early retirement, or shift to covering only current expenses and trade speed for freedom of work choice now.
- Evidence: Plausible mechanism, limited direct outcome data.
- Avoid: Treating Coast FI as permission to reduce savings below covering current expenses — coasting means not adding to the portfolio, not drawing from it.
Why it works
Coast FI reframes the accumulation journey by separating the compounding function from the savings function. Once you reach Coast FI, investment growth alone will carry the portfolio to full FI by a target age — you no longer need to save, only to cover current expenses. This milestone is typically reached much earlier than full FI and creates a genuine choice point: continue the high savings rate for early retirement, or shift to covering only current expenses and trade speed for freedom of work choice now.
How to do it
- 1Calculate your full FI number (25x target retirement spending).
- 2Calculate how many years until traditional retirement age (say, 65).
- 3Use a compound interest calculator to find the amount needed today to grow to full FI by that date at your expected real return.
- 4That amount is your Coast FI number — a reachable intermediate target.
What the evidence says
MechanisticCoast FI is a mathematical construct derived from compound growth formulas; its motivational value as a milestone is supported by goal-gradient research on intermediate goals.
Honest caveat: Coast FI assumes a fixed real return, which is uncertain. It also requires not withdrawing from the portfolio during the coasting period, which requires living on earned income alone.
Common mistake
Treating Coast FI as permission to reduce savings below covering current expenses — coasting means not adding to the portfolio, not drawing from it.
IX Coach calculates your Coast FI alongside your full FI number, showing you both milestones and the different life choices each one enables.
Practice this with IX Coach →