What is a FIRE number?
Your FIRE number is the amount you need invested to retire: your annual expenses divided by your safe withdrawal rate. With the classic 4% rule, a $40,000/year lifestyle needs $1,000,000 invested.
The safe withdrawal rate
The 4% rule says you can withdraw 4% of your portfolio in year one, then adjust for inflation each year, and historically have a high chance of not running out over 30 years. More conservative planners use 3–3.5% for longer retirements or uncertain markets.
How the calculator works
It compounds your current savings plus monthly contributions at your expected return until your retirement age, then compares that projected balance to your FIRE number. The gap tells you whether you need to save more, retire later, or reduce planned spending.
Reading your result
- Positive gap — you're projected to exceed your number. Nice.
- Negative gap — increase contributions, extend your timeline, or lower your expenses.
Note: results use a constant nominal return. Real planning should also account for inflation (try a "real" return of ~5–6% to roughly model inflation-adjusted growth).
Related tools
- Compound interest calculator — the growth engine behind this.
- Savings goal calculator — hit smaller milestones first.