FIRE Calculator

The FI number is the nest egg that funds your spending: annual expenses divided by the safe withdrawal rate. At a 4% withdrawal rate you need 25 times your annual expenses, because spending 4% of a portfolio is the mirror image of needing 25 times the income. Lower the withdrawal rate and the target rises sharply — 3% means roughly 33 times expenses.

Years to FIRE compounds your current savings and your monthly share of the annual savings rate at a monthly equivalent of the expected real return. Real return matters: it is the return left after inflation, so the projection stays in today's purchasing power. The projection stops at 80 years and reports 80+ when the target is out of reach on those assumptions, which usually means the savings rate or the spending target has to move.

Coast FIRE runs the question backwards. It asks how much you would need invested today so that growth alone reaches your FI number by the time you would otherwise arrive, with no further contributions — the point at which saving stops being mandatory. The safe withdrawal amount closes the loop: it is the income your FI number can generate each year.

Compound Interest Formula

Assumptions

• Interest compounds monthly (n=12)
• Contributions made at end of each month
• Rate remains constant over entire period
• No taxes or fees deducted

This calculator provides estimates only. Actual investment returns vary and may result in loss of principal.