Calculated answer
$172,784
At 3.5% spending support, $40,000 of annual retirement expenses points to a simple FIRE number of $1,142,857. Discounted back 30 years at 6.5%, the coast FIRE threshold is $172,784, so this scenario is $122,784 short of the coast target.
- Coast FIRE number
- $172,784
- Full FIRE number
- $1,142,857
- Current invested assets
- $50,000
- Amount below coast target
- $122,784
Coast FIRE number = FIRE number ÷ (1 + return)^years until retirement
The example first estimates the full FIRE number from annual spending, then discounts that target back to today using the expected annual return and years until retirement.
- Estimate the full FIRE target from $40,000 of annual spending and a 3.5% withdrawal rate.
- Count 30 years from age 30 to age 60.
- Discount the future FIRE target back at 6.5% annual growth.
- Compare the resulting $172,784 coast target with the current $50,000 invested balance.
What this coast FIRE example is testing
The question is whether $50,000 already invested could plausibly compound into a future retirement target by age 60 if contributions slowed or stopped.
This is a simplified framing tool. Real outcomes depend on taxes, fees, actual returns, spending changes, and whether contributions continue in practice.
How spending assumptions change the answer
Annual retirement spending of $40,000 is the main driver of the future FIRE number. Higher spending raises the target and usually makes coast FIRE harder to reach.
Small changes in the withdrawal rate or retirement age can also change the coast threshold materially because the invested balance has more or less time to compound.
A more modest annual spending target keeps the underlying FIRE number, and therefore the coast threshold, lower than a higher-spending version of the same scenario.