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.

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

1. Calculate your full FI number (25x target retirement spending).
2. Calculate how many years until traditional retirement age (say, 65).
3. Use a compound interest calculator to find the amount needed today to grow to full FI by that date at your expected real return.
4. That amount is your Coast FI number — a reachable intermediate target.

Evidence

Coast 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. (mechanistic)

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.