What a FIRE number actually means

FIRE stands for Financial Independence, Retire Early. The core idea is that once your investments are large enough to cover your annual expenses through a modest yearly withdrawal, you no longer need a paycheck to live on. This calculator finds that number for you, then works out how many years of saving at your current rate it would take to reach it.

The safe withdrawal rate you choose has an outsized effect on your FIRE number, more than most people expect. A lower withdrawal rate is more conservative and produces a larger target, since it assumes you want your balance to last through a longer or less predictable retirement. It is worth testing a few different withdrawal rates to see how much that single number moves your timeline. To see how a fixed monthly contribution compounds on its own without a specific end target, our compound growth calculator shows that clearly.

The 4 percent withdrawal rate that shows up as the default here comes from long running academic research on how much a retirement portfolio can sustainably support, most notably the Trinity study from Trinity University. It is a widely cited starting point, not a guarantee, and reasonable people choose different rates depending on how conservative they want to be. You can read a summary of that research and its limitations on investor.gov.