FIRE Calculator
Enter your monthly expenses, current savings, and monthly investment to see your FIRE number (25× expenses), years to financial independence, savings rate, percent funded, passive income your savings generate today, and how many years $500/month extra saves.
Your savings rate matters more than your salary — saving 50% reaches FIRE in ~17 years at any income level; saving 10% takes 40+ years.
25×
The FIRE multiplier: 25× annual expenses = your FIRE number (1 ÷ 4% = 25)
50%
The FIRE target savings rate — at 50% savings rate, timeline is ~17 years regardless of income
17yr
Years to FIRE at 50% savings rate — drops from 40+ years at 10%, proving savings rate beats salary
The math behind financial independence
Why FIRE is a savings rate game, not an income game.
Savings rate beats income — every time
A high earner saving 5% and a modest earner saving 50% both spend 95% or 50% of their cash flow respectively — but their FIRE timelines are radically different: 66 years vs 17 years. The math is self-reinforcing: cutting expenses reduces the FIRE target AND raises the savings rate simultaneously, compressing the timeline from both ends.
The 4% rule: 25× for a reason
William Bengen's 1994 research — and the Trinity Study in 1998 — found that withdrawing 4% of a diversified portfolio annually had a 95%+ success rate over every 30-year period from 1926–1992. Your FIRE number is 25× annual expenses because 1 ÷ 4% = 25. At $4,000/month ($48,000/year), that's $1,200,000 — a precise, research-backed target, not a round estimate.
Lean FIRE, Fat FIRE, and Coast FIRE
Lean FIRE: retire on $25–40k/year ($625k–$1M target). Fat FIRE: keep a high-spending lifestyle at $80–150k/year ($2M–$3.75M target). Coast FIRE: save enough early that compound growth carries you to FIRE without another dollar contributed. This calculator computes full FIRE. Use the Coast FIRE calculator for the coasting scenario.
How the FIRE Calculator Works
Formula
FIRE Number = Monthly Expenses × 12 × 25
(25× because 1 ÷ 4% = 25 — the 4% safe withdrawal rule)
Savings Rate = Monthly Investment ÷ (Monthly Investment + Monthly Expenses) × 100
(FIRE movement standard — income-independent)
Month-by-month simulation until balance ≥ FIRE Number:
Balance(m+1) = Balance(m) × (1 + AnnualReturn/100/12) + Monthly Investment
yearsToFire = months ÷ 12 (capped at 100 if never reached)
Passive Income Now = Current Savings × 0.04 ÷ 12
(monthly income at 4% withdrawal applied to today's balance)
+$500/mo Saves = yearsToFire(current) − yearsToFire(current + $500/mo)Enter your monthly expenses
Total monthly spending — housing, food, transport, subscriptions, everything. This single number drives your FIRE number ($4,000/mo → $1,200,000) and the denominator of your savings rate. Reducing expenses is the most powerful lever: it cuts the target AND raises the savings rate simultaneously.
Enter current savings
Total invested assets today — index funds, 401(k), IRA, taxable brokerage accounts. Not home equity, emergency cash, or a savings account. Default $50,000 already generates $167/month in passive income at the 4% rule, and covers 4.2% of a $1,200,000 FIRE number.
Set your monthly investment
How much you add to investments each month. At $2,000/month with $4,000 in expenses, your savings rate is 33.3% — above average, but below the 50% FIRE target. Every $500 more per month cuts roughly 2 years off the default 19.6-year timeline.
Choose expected annual return
7% is the S&P 500's long-run inflation-adjusted average (Vanguard Capital Markets Model 2024: 6.9–7.9%). Use 5–6% for a conservative projection (mixed bonds/equities). The simulation runs monthly at AnnualReturn/12 per month.
Read all six outputs
FIRE number (25× annual expenses), years to FIRE (month simulation), savings rate (investments ÷ cash flow), percent funded (current savings as % of FIRE number), passive income now (what current savings generate today at the 4% rule), and years saved by adding $500/month.
At the default inputs — $4,000/month expenses, $50,000 current savings, $2,000/month invested, 7% return — the calculator produces a $1,200,000 FIRE number reached in 19.6 years, with a 33.3% savings rate. Your $50,000 in current savings already generates $167/month in passive income under the 4% rule. Adding $500/month accelerates the timeline by approximately 2.1 years.
The 4% rule (Bengen 1994, Trinity Study 1998) underpins the FIRE number calculation: a 4% annual withdrawal from a 50/50 diversified portfolio has historically succeeded over every 30-year period since 1926 with 95%+ probability. FIRE number = 25× annual expenses because 1 ÷ 4% = 25. A more conservative 3.5% withdrawal (28× expenses) is appropriate for 40+ year retirements.
Savings rate is calculated as investments ÷ (investments + expenses) — the FIRE movement standard. This definition is income-independent: a person earning $60k/year who saves $2,000/month and spends $4,000/month has the same 33.3% savings rate as a person earning $300k/year doing the same. At 50%, the timeline is roughly 17 years regardless of salary. This is why FIRE practitioners focus on controlling spending, not just growing income.
Frequently Asked Questions
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