How it works
Your FI number is the invested amount at which a safe withdrawal rate covers your yearly spending: $52,000 a year at 4% needs $1,300,000. Each year your investments grow by the return you enter (after inflation, so everything stays in today's dollars) and that year's savings are added at the end. Years to FI is the first whole year the balance reaches the FI number. Coast FI is the amount that would grow to your FI number by 65 with no more saving.