FIRE calculator

How this calculator works

This calculator estimates a financial independence (FIRE) target and a simplified timeline for reaching it. The FIRE number equals annual retirement spending divided by a target withdrawal rate—for example, $50,000 per year divided by 4% equals a $1.25 million portfolio target.

The timeline projection compounds your current invested assets and monthly contributions at a constant real return, meaning return after inflation. Results are expressed in today's purchasing power so the target spending figure and projected balance remain comparable over time.

The funded percentage shows how much of the target your current assets represent. The remaining gap and projected years to reach the target depend entirely on the spending, withdrawal rate, contribution, and return assumptions you enter. This is a planning framework, not a guarantee that work can stop on a specific date.

What affects the result

Small changes in assumptions can shift the FIRE number and timeline dramatically.

• Annual spending target — Every $10,000 of annual spending adds roughly $250,000 to the target at a 4% withdrawal rate. Use realistic retirement spending, not necessarily today's budget.
• Withdrawal rate — A 4% rate implies a 25× spending multiplier. A more conservative 3.5% rate implies roughly 28.6×, raising the target for the same spending.
• Current investments — Existing assets shorten the timeline through compounding. Starting from $0 vs. $200,000 changes the path even with identical contributions.
• Monthly contributions — Higher savings rate is often the most controllable lever. Increasing contributions by $500 per month can shave years off the timeline depending on return assumptions.
• Real return assumption — A 5% real return produces a faster timeline than 4% on the same inputs. Real returns are uncertain and vary by asset allocation and time period.
• Taxes and fees — Taxable vs. tax-advantaged accounts, investment fees, and healthcare costs are not fully modeled here but reduce safe spending in practice.

The 4% rule originated from historical U.S. stock/bond research. It is a starting point with limitations—not a promise that every portfolio survives every retirement horizon.

Real-world examples

1. Basic FIRE number. Annual spending of $50,000 divided by a 4% withdrawal rate produces a $1.25 million target. At a 3.5% rate, the same spending requires about $1.43 million—an $180,000 difference from a half-point rate change.

2. High saver, moderate spending. A 35-year-old with $150,000 invested, $3,000 monthly contributions, $40,000 annual spending target, 4% withdrawal rate, and 5% real return may reach the target in roughly 15–20 years in this simplified model—far earlier than traditional retirement age if assumptions hold.

3. Coast FIRE crossover. Once invested assets reach the coast threshold—enough to grow to the FIRE number without future contributions—mandatory savings pressure eases even if full FIRE has not arrived. Use the Coast FIRE calculator to estimate that lower bar.

4. Conservative planner. Same $50,000 spending with a 3.25% withdrawal rate implies about $1.54 million. Testing multiple withdrawal rates shows how sensitive the plan is to conservative vs. optimistic assumptions.

Common mistakes

• Using current spending without adjusting for retirement changes. Housing, commuting, and payroll taxes may fall; healthcare and leisure may rise. Build a retirement-specific budget.
• Mixing nominal returns with today's-dollar spending. Nominal 7% with 3% inflation is not the same as 4% real. Keep assumptions consistent.
• Treating the 4% rule as universal or guaranteed. Horizon, allocation, sequence of returns, and flexibility all affect safe withdrawal rates.
• Excluding taxes and irregular large expenses. Roth vs. traditional account mix, capital gains, and one-time costs change spendable income.
• Ignoring other income sources. Social Security, pensions, rental income, or part-time work reduce the portfolio burden but add complexity.
• Planning for a single optimistic scenario. Stress-test with lower returns, higher spending, and higher withdrawal rates before treating a date as firm.

When to use this calculator

Use this calculator when exploring financial independence as a planning target—testing how spending goals, savings rate, and investment assumptions interact over time.

It helps answer whether your current path is on track, how much a spending cut or savings increase accelerates the timeline, and how sensitive the target is to withdrawal rate choice. Pair it with the Coast FIRE calculator for partial independence milestones, the retirement projection calculator for age-based accumulation modeling, and the retirement withdrawal calculator to stress-test spending after you reach the target.

Revisit inputs when income, spending, or market assumptions change materially.

Related calculators

Estimate the lower Coast FIRE threshold with the Coast FIRE calculator. Project retirement savings by age using the retirement projection calculator. Stress-test withdrawal sustainability with the retirement withdrawal calculator. Quantify fee drag on the path to FIRE with the investment fee calculator.