Free tool, no account
Your FIRE number, your date, and the odds.
Enter what you have, what you save, and what retirement costs. The calculator returns the portfolio that covers that spending, the age you reach it, and how often the portfolio lasts to 95 across 1,000 simulated markets. Copy the link and the numbers come back exactly.
How the numbers are made
Three calculations, one set of engines.
Nothing here is a rule of thumb dressed up as a projection. The number, the date and the odds each come from the code that runs the Retirement tab inside Promi, with your inputs standing in for linked accounts.
The number
Annual spending divided by the withdrawal rate. At 4%, $60,000 a year needs $1.5 million; at 3.5% it needs about $1.71 million. The rate is the whole argument, so it is a slider, not a constant.
The date
Savings compound monthly at the real return, which is (1 + return) / (1 + inflation) minus 1, not return minus inflation. Contributions and spending stay flat in today's dollars, so the date is honest about purchasing power.
The odds
1,000 market paths drawn from a lognormal distribution at the volatility you set, each retiring at the projected age and drawing your spending until 95. The percentage is how many paths never ran out. The seed is your inputs, so a shared link reproduces the same fan.
Coast FIRE is the same engine viewed from the other end: the amount that, invested today and left alone, grows to the FIRE number by your chosen retirement age. Switch modes in the calculator to see it, and to see the odds for that plan with contributions stopped.
The same projection, on your real accounts.
Promi links your banks and runs this engine on your actual balances, contributions and spending, with taxes, Social Security and a historical backtest alongside the Monte Carlo.
Try the interactive demo