FIRE Number Calculator

How to use

1. 1Pick a mode: FIRE number (target from expenses and SWR), Time to FI (years to reach FIRE), or Coast FIRE (portfolio today that grows untouched to FIRE).
2. 2Enter your annual expenses in today's dollars. Choose Lean (0.5x), Regular (1x), or Fat (1.5x) to scale the base expenses.
3. 3Pick a safe withdrawal rate. Use 4% for the classic 25x rule, 3.5% or lower for a more conservative number, or select Custom SWR to type your own rate.
4. 4For Time to FI and Coast FIRE, enter your current portfolio, monthly contribution, expected nominal return, and inflation rate. The tool converts these into a real return automatically.
5. 5Coast FIRE also needs your current age and target retirement age. Time to FI accepts an optional current age so the result can show your projected retirement age.
6. 6Read the headline result, the comparison table, and the year-by-year schedule, then use Copy summary or Copy schedule CSV to save the breakdown.

About this tool

FIRE Number Calculator answers the three questions every person searching for early retirement wants in one place. First, it computes your FIRE number, the portfolio amount that lets you stop working: target = annual expenses divided by the safe withdrawal rate. At a 4% SWR (the classic Trinity Study rate) this is the 25x annual expenses rule, at 3.5% it is about 28.57x, and at 3% it is about 33.33x. A live comparison table shows the FIRE number at 5%, 4%, 3.5%, 3.25%, and 3% SWRs so you can see the impact of switching to a more conservative assumption. Lean / Regular / Fat presets scale your base expenses by 0.5x, 1x, and 1.5x so all three flavors of FIRE are visible side by side at your chosen withdrawal rate. Second, it projects time to FI: given your current portfolio, monthly contribution, and expected real return, it finds the exact month your balance reaches the FIRE number. The math is the standard ordinary-annuity future value formula, solved by binary search on the integer month. A real (inflation-adjusted) rate is used internally via the Fisher equation so the FIRE number stays in today's dollars throughout the projection. A year-by-year schedule shows contributions, growth, and ending balance at each age. Third, it computes Coast FIRE: the portfolio amount you need today so that pure growth, with zero further contributions, reaches the FIRE number by your target retirement age. The result includes the Coast FIRE age, the point at which you can stop contributing and let compounding finish the job. Currency selection covers USD, EUR, GBP, CAD, AUD, JPY, INR, and TRY for display formatting through Intl.NumberFormat with no FX conversion. Everything runs in your browser; nothing is sent to a server. This is a planning model, not financial advice: it does not account for sequence-of-returns risk, taxes, healthcare, pensions, or social security, and long-term retirement decisions should be confirmed with a qualified fiduciary.

Free to use. Works in your browser. No signup, no login.