Your savings rate decides your freedom date. Not your salary, not your inheritance, not your luck. At a 25% savings rate: 32 years before your wealth covers your expenses for life. At 50%: 17 years. At 70%: 8.5 years. That's FIRE (Financial Independence, Retire Early), a movement born in the 1990s with Vicki Robin and popularized in 2010 by Mr. Money Mustache. An equation, not a promise.
FI (Financial Independence) = your wealth generates enough passive income (dividends, interest, withdrawals) to cover your expenses indefinitely. RE (Retire Early) is optional: many “independents” keep working, but on their own terms. The real freedom of FIRE isn't idleness. It's choice. You work if you want to, not because you have to.
If you save X% of your income and invest at 5% real/year, your time to FI is almost independent of salary. At 10% savings: 51 years. At 25%: 32 years. At 50%: 17 years. At 70%: 8.5 years. At 90%: 3 years. Why? When you save more, two things happen at the same time: (1) your wealth grows faster and (2) your target expenses shrink, so the FIRE Number you need to reach also drops. Hence FIRE's absolute priority: optimize your savings rate before anything else.
A single universal rule: Expenses × 25 = FIRE Number. Four ways to get there.
Marie saves 50% of her income ($1,500/month) and invests in a global ETF at 5% real return. Her annual expenses: $18,000. Her FIRE Number: 18,000 × 25 = $450,000. At $1,500/month × 12 = $18,000/year invested at 5% compound, she reaches $450,000 in roughly 17 years, so at age 47. If she only saved 25% ($750/month), her expenses would rise to $27,000/year and her FIRE Number would climb to 27,000 × 25 = $675,000: it would then take ~32 years, meaning age 62. That is the double mechanics of FIRE: saving less slows accumulation AND raises the target. The savings rate is the only lever that radically changes the trajectory.
Three classic traps to avoid from day one.
Four simple steps to move from theory to action.