Savings Rate

If you take home $5,000 a month and put $2,000 of it into savings and investments, your savings rate is 40%. It matters more than almost anything else in FIRE math, because it works two ways at once: a higher savings rate means you're adding more to your portfolio and you need less income to sustain your (smaller) spending once retired. That double effect is why savings rate, not income, tends to predict how fast someone reaches financial independence.

At a 10% savings rate, reaching FIRE can take 40+ years. At 50%, it often takes around 17 years. At 70%, under 10 years. The jump from 20% to 50% cuts the timeline dramatically more than most people expect — which is why FIRE advice leans so heavily on this one number.