Question 1

What is a "FIRE number"?

Accepted Answer

FIRE (Financial Independence, Retire Early) number is the total invested assets you'd need so that a safe withdrawal from them, combined with any guaranteed income like Social Security or a pension, is intended to support your retirement spending under an assumed withdrawal rate. It's calculated as your annual income gap divided by your safe withdrawal rate. For example, someone with a $50,000 annual income gap using a 4% safe withdrawal rate would need a FIRE number of $1,250,000 ($50,000 ÷ 0.04) — the invested balance that, at a 4% annual draw, provides that first-year draw, without a guarantee that it lasts indefinitely.

Question 2

Why does my savings rate matter more than my income?

Accepted Answer

Your savings rate — the percentage of income you save, not the raw dollar amount — determines both how fast you build your FIRE number and how large a FIRE number you actually need (since a higher savings rate typically means living on less, which lowers your target). Two people with very different incomes but the same savings rate will often reach financial independence in a similar number of years. For example, someone earning $60,000 and saving 50% of it lives on $30,000 and needs a FIRE number sized to replace only $30,000 of annual spending, while someone earning $150,000 but also saving 50% needs a much larger FIRE number — yet both reach financial independence in roughly the same number of years, since the savings rate, not the income level, drives the timeline.

Question 3

What is "Coast FIRE"?

Accepted Answer

Coast FIRE means you've saved enough already that, left untouched, compound growth alone will grow your balance to your full FIRE number by traditional retirement age — even if you stop actively contributing. It lets you shift to lower-paying but more enjoyable work, or reduce your savings rate, without derailing your long-term retirement date. For example, a 30-year-old with $300,000 already invested who needs $1.5 million by age 65 could stop contributing entirely and still reach that target through compound growth alone at a reasonable return — freeing them to take a lower-paying, more fulfilling job without pushing back their retirement date.

Question 4

How reliable is this projection?

Accepted Answer

It assumes a constant savings rate and constant investment return every year, which real life rarely matches exactly. Treat the projected retirement age as a planning estimate to revisit annually — a raise, a market downturn, or a change in expenses can shift it meaningfully in either direction. For example, a projection based on a steady 7% return and a fixed savings rate could shift by several years in either direction if a market downturn hits early, a raise increases the savings rate, or expenses change — which is why this calculator's output is best treated as a planning estimate to revisit annually rather than a fixed date.

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