FIRE Calculator — Financial Independence, Retire Early

The FIRE number

FIRE stands for Financial Independence, Retire Early. The core idea is a portfolio large enough that its returns can pay for your life indefinitely. The standard formula is FIRE number = annual expenses ÷ safe withdrawal rate. With a 4% rate, expenses of 40,000 a year require a portfolio of 1,000,000 — exactly 25 times your yearly spending. A lower withdrawal rate gives a bigger, safer target; a higher rate gives a smaller, riskier one. Because spending is the input, cutting expenses helps twice: it raises the amount you can save and lowers the target you need.

Years to financial independence

The calculator grows your savings month by month. Each month the balance is multiplied by (1 + real return)^1/12 and one twelfth of your annual contribution is added. It counts the months until the balance reaches your FIRE number, then shows the time and the age at which that happens. The yearly projection lists contributions, growth and balance so you can see compounding take over. Returns are entered as real returns, meaning after inflation, which keeps all results in today's purchasing power. If your contribution is too small or the target too large, the tool reports that FI is not reached within 100 years.

Lean, Fat and Coast FIRE

Lean FIRE targets a frugal lifestyle (70% of your expenses here) and usually arrives sooner. Fat FIRE targets a more comfortable one (150%) and takes longer. Coast FIRE asks a different question: how much do you need now so that, with no more contributions, growth alone carries you to your FIRE number by a traditional retirement age? The formula is Coast number = FIRE number ÷ (1 + real return)^{years to retirement age}. Once your savings exceed it, you only need to earn enough to cover current living costs. These are simplified estimates that ignore taxes, fees, sequence-of-returns risk, pensions and healthcare costs. This is an educational tool, not financial advice.