FIRE Number Calculator

• Calculates the FIRE number from annual expenses and a chosen safe withdrawal rate.
• Projects the time to reach that number from current investments and monthly contributions.
• Optionally shows a Coast FIRE reference point — what would need to be invested today to reach the goal by a traditional retirement age with no further contributions.
• Compares the FIRE number needed across a range of withdrawal rate assumptions.

How to use this calculator

Enter expected annual expenses in retirement (in today's dollars), a safe withdrawal rate, current investments, and a monthly contribution amount along with an expected annual return. Adding a current age unlocks a projected age at financial independence and a Coast FIRE reference point.

How the FIRE number is calculated

The FIRE number is the amount that, at the chosen withdrawal rate, would need to be withdrawn each year to cover expenses indefinitely:

FIRE number = annual expenses ÷ safe withdrawal rate

At a 4% withdrawal rate, this is the same as multiplying annual expenses by 25 — the classic "25x expenses" rule of thumb is just this formula rearranged. A more conservative 3.5% rate produces a larger number (about 28.6x expenses), built in as extra safety margin.

A worked example

$48,000 in annual expenses at a 4% withdrawal rate produces a FIRE number of $1,200,000. Starting from $50,000 already invested, contributing $1,500 a month at a 7% expected return, that target is projected to be reached in roughly 22 years.

What is Coast FIRE?

Coast FIRE describes having enough already invested that growth alone — with no further contributions — would reach the full FIRE number by a normal retirement age, typically referenced against age 65. It's a useful checkpoint even for someone who plans to keep contributing: reaching Coast FIRE means the retirement outcome is largely secured by market growth from that point forward, and any further contributions accelerate the timeline rather than being strictly required.

Assumptions and limitations

• Uses a flat expected return and withdrawal rate. Real markets vary year to year, and a string of poor returns early in retirement (sequence-of-returns risk) can matter more than the long-run average.
• Expenses are held in today's dollars for the FIRE number itself, with a separate inflation- adjusted note shown for reference — the actual withdrawal target should rise with inflation over time.
• Doesn't model taxes on withdrawal, which depend heavily on account type (taxable brokerage, traditional retirement account, or Roth) and vary by individual situation.

Common mistakes

Using a withdrawal rate without understanding its history. The 4% figure comes from historical backtesting over specific past market periods and isn't a guarantee of future results — some planners now recommend a somewhat lower rate for extra safety, especially for a very long retirement.

Forgetting expenses will likely change over decades. Healthcare costs often rise faster than general inflation as people age, while other expenses (a mortgage paid off, fewer dependents) may fall — the flat annual expense figure here is a simplification of what's often a changing picture.

Ignoring sequence-of-returns risk near the target date. A market downturn in the first few years after reaching a FIRE number and beginning withdrawals can do outsized damage compared to the same downturn happening later — this calculator's steady-return model doesn't capture that risk.

Frequently asked questions