The calculators
Coast FIRE calculator
How much you need invested today for compounding alone to reach your number by your retirement age.
Safe withdrawal rate calculator
Turn a portfolio into a first-year retirement income, or an income target into the portfolio it needs.
Investment fee calculator
What a 1% fee removes over decades, and how a flat subscription compares.
What a calculator cannot tell you
Every calculator on this page runs one path at a single assumed return. That is useful for sizing a problem and useless for judging risk, because it silently assumes markets deliver the average every year — which they never do.
The gap between a calculator and a simulation is the difference between "you will have $2.4 million" and "half of the futures we simulated ended above $2.4 million, one in ten ended below $900,000, and the plan ran out of money in 6% of them". If the second framing is what you need, the live demo runs the full engine on a sample household with no account.