FIRE Calculator

The FIRE (Financial Independence, Retire Early) calculator determines how long it takes for your investment portfolio to reach a target amount — your FIRE Number. Your FIRE Number equals your annual expenses divided by your safe withdrawal rate (typically 4%, based on the Trinity Study). Each year, your savings grow by the real return (investment return minus inflation) plus your annual savings (income minus expenses). Once your portfolio reaches the FIRE Number, you can theoretically live off investment returns indefinitely.

The concept of financial independence has evolved from a niche personal finance idea into a mainstream movement affecting millions of workers worldwide. A 2023 Bankrate survey found that 55% of American workers feel behind on retirement savings, and the median retirement savings for households aged 55-64 is only $134,000 — far short of what most financial planners recommend. The FIRE framework provides a structured, mathematical approach to answering the most fundamental question in personal finance: 'When can I stop working?' The power of the FIRE calculation lies in its simplicity and its sensitivity to the savings rate variable. Most people intuitively understand that earning more or spending less helps retirement, but few grasp the mathematical relationship: increasing your savings rate from 20% to 40% does not merely cut your working years by half — it can reduce them by 60% or more because the savings rate simultaneously increases contributions while reducing the target number. This non-linear relationship is one of the most important insights in personal finance. For many people, running this calculation for the first time is genuinely life-changing. Seeing that financial independence is achievable in 15-20 years rather than the assumed 40+ motivates fundamental behavioral changes. Even for those who do not pursue aggressive early retirement, understanding your FIRE number provides a concrete financial target that makes abstract goals like 'saving enough' measurable and actionable.

Scenario 1: The High-Income Late Starter — A 40-year-old software engineer earns $180,000/year and spends $100,000. With $200,000 already saved and a 7% real return, her FIRE number at 4% withdrawal is $2,500,000. The calculator shows she reaches FIRE at age 55 — saving $80,000/year with compound growth gets her there in 15 years. If she reduces spending by $10,000/year, the FIRE number drops to $2,250,000 and she reaches it at 53 — two years earlier from a single adjustment. Scenario 2: The Lean FIRE Couple — A couple aged 30 earns a combined $90,000 and has optimized expenses to $30,000/year. Their FIRE number is $750,000. Starting from $50,000 in savings with $60,000 annual contributions at 7% return, they reach FIRE at age 40 — just 10 years. Their 67% savings rate is the key driver, not their income. A couple earning $200,000 with the same $60,000 savings and $140,000 spending would need $3,500,000 and not reach FIRE until 55. Scenario 3: Coast FIRE Milestone — A 28-year-old has accumulated $150,000 in index funds. At 7% real return, this grows to approximately $1,140,000 by age 58 — enough for traditional retirement spending of $45,000/year at 4% withdrawal. He has achieved Coast FIRE: he no longer needs to save for retirement and can pursue lower-paying but more fulfilling work, knowing compound growth is handling the rest.

1. Using pre-tax income for savings rate calculation — Your true savings rate should be based on take-home pay. Someone earning $100,000 who saves $30,000 does not have a 30% savings rate if taxes take $25,000 — their real savings rate based on disposable income is 40% ($30,000 / $75,000). Using pre-tax calculations understates your actual progress. 2. Ignoring sequence-of-returns risk — The order of investment returns matters enormously in the first 5-10 years of retirement. A 30% market crash in year one of retirement is far more devastating than one in year 20, because withdrawals compound the loss. This is why many FIRE planners use a 3.5% withdrawal rate or maintain a cash buffer covering 2-3 years of expenses. 3. Underestimating lifestyle inflation — Many FIRE planners calculate their number based on current expenses but gradually increase spending as income rises. A person targeting $40,000/year expenses who slowly drifts to $60,000 has inadvertently increased their FIRE number from $1M to $1.5M, adding years to their timeline without realizing it. 4. Not accounting for major future expenses — FIRE calculations based on current annual expenses often miss large irregular costs: home repairs ($10,000-$50,000), vehicle replacement ($30,000+), children's education, parental care obligations, or medical emergencies. Add 10-15% to your calculated annual expenses as a buffer for these predictable surprises. 5. Assuming constant investment returns — Historical 7% real returns are an average over long periods, but individual years vary wildly. A decade of below-average returns early in the accumulation phase can delay FIRE significantly. Stress-test your plan with conservative assumptions (5% real return) to ensure resilience.