How does having a paid-off house change my FIRE number and withdrawal math?

A paid-off home removes the mortgage from your annual spending, which lowers your FIRE number by 25x that payment at a 4% rate. Eliminating a $2,000 monthly payment ($24,000 a year) can shrink your target by roughly $600,000. It also reduces sequence-of-returns risk because your fixed housing cost no longer forces withdrawals in a down market.

The nuance: property taxes, insurance, and maintenance remain and tend to rise with inflation, so budget those into your ongoing expenses. Also weigh the opportunity cost, since money used to prepay a low-rate mortgage could have grown in the market. For many FIRE seekers, entering early retirement mortgage-free is more about spending stability and peace of mind than pure return maximization.