Because your FIRE number is 25x your annual expenses (at a 4% safe withdrawal rate), and that multiplier is unforgiving — every $1,000 you spend per year requires $25,000 invested to support it. The fastest lever is annual expenses: a $5,000/yr lifestyle cut reduces your target by $125,000 AND frees up that money to invest. Inflation also matters: your number is shown in future dollars at retirement, which can look shockingly large; the “today’s dollars” figure under the headline shows the equivalent in current purchasing power.

The Trinity Study (1998) showed a 4% withdrawal rate gave high success odds over a 30-year retirement using historical US market returns. For longer retirements (40+ years, common with FIRE), the safe rate drops — this calculator auto-adjusts to 3.5% for 31-40 years and 3% for 40+ years. Critics also note that future returns may be lower than the 20th-century average, and sequence-of-returns risk in the first 5 years matters more than the long-run average. Treat the SWR as a planning starting point, not a guarantee.

Pull 12 months of credit card and bank statements, sum them, and subtract savings/investments and any one-off purchases that won’t recur. Don’t use your budget — use what you actually spent. Most people underestimate by 15–25% because they forget annual or quarterly costs (insurance, property tax, car maintenance, travel). For this calculator, enter base lifestyle expenses without child-related costs — dependents are modeled separately and drop out of the calculation at age 18.

7% nominal (4% real after inflation) is the conventional default for a 100% stock portfolio based on US historical averages. A 60/40 stock/bond portfolio is closer to 5–6% nominal. International equities, bonds, and cash all return less. If you’re planning conservatively, use 5–6%; if you’re stress-testing, use 4%. Lower returns extend the timeline non-linearly — small drops in assumed return have outsized effects on long-horizon plans.

For most people retiring at 65 or later, yes — ignoring SS forces you to over-save. For early retirees with a long gap before SS starts (62 at the earliest, often 67), the bridge years dominate the FIRE number, so SS only shaves a partial amount off. This calculator handles both partners independently: each benefit applies only from its own claiming age, so a couple with staggered claiming ages is modeled correctly. Look up your projected benefit at ssa.gov; younger workers should be conservative since future benefit levels are politically uncertain.

Coast FIRE is the portfolio value where compound growth alone will reach your full FIRE number by your target retirement age — with zero further contributions. Once you hit it, you can switch to a lower-paying or part-time job that just covers current expenses, and your investments quietly grow themselves to retirement. The KPI tile shows the threshold; the message below tells you how far away you are. Even if you intend to keep saving, hitting Coast FIRE is a significant psychological milestone: it means you have the option to slow down.

It doesn't model: taxes (federal, state, capital gains, RMDs), sequence-of-returns risk in early retirement, healthcare cost spikes before Medicare eligibility, market-crash scenarios, real estate equity, inheritance, employer matching, asset location optimization (which accounts to fund first), or major one-time costs (kids' college, weddings, home purchases beyond what’s in your base expenses). Treat the result as a high-level target. The closer you get to actual retirement, the more these omitted factors matter — a fee-only fiduciary advisor is worth the consultation for the final plan.