What is a FIRE calculator?
A FIRE calculator estimates how long it could take for a portfolio to reach a financial-independence number. This NumberMotive version compares a projected portfolio, grown with monthly compounding, with a FIRE number from annual spending and a withdrawal rate you type.
The result is an educational estimate from the numbers you type. It is not financial advice, retirement advice, a guaranteed independence date or a recommendation to invest.
How financial independence is modeled here
The FIRE number is annual spending divided by the withdrawal-rate decimal. The portfolio then grows with the same monthly compounding model used by Compound Interest, Retirement Growth and Investment Growth. The worksheet looks for the first whole month, from 0 through 1,200, when that projected balance is at least the FIRE number.
Taxes, inflation, Social Security, sequence-of-returns risk and a recommended portfolio are outside this worksheet.
The formulas this calculator uses
FIRE number = annual spending target ÷ (safe withdrawal rate ÷ 100). With $60,000.00 of spending and a 4% rate, the number is $1,500,000.00.
Monthly rate = (expected annual return ÷ 100) ÷ 12.
Projected portfolio after n months uses the current portfolio grown by that monthly rate, plus monthly contributions grown by the same rate. If the return is 0%, the projection is the current portfolio plus contributions times n. If the contribution is $0.00, only the current portfolio grows.
Years needed = months to the first crossing ÷ 12, only when that crossing happens within 100 years. The calculator does not return NaN or Infinity.
Worked example
With a $100,000.00 current portfolio, a $1,000.00 monthly contribution, a 7% expected annual return, $60,000.00 of annual spending and a 4% withdrawal rate, the FIRE number is $1,500,000.00.
Monthly compounding first reaches that number at month 313, which this worksheet shows as 26.08 years. The projected portfolio at that month is about $1,504,675.91. None of those inputs is a recommended savings plan, return or withdrawal rate.
What this calculator does not include
- Taxes, inflation or fee adjustments
- Social Security or pension income
- A guaranteed retirement date or success rate
- A recommended withdrawal rate, contribution or portfolio
- Automatic tracking or saved history
Limitations of this calculator
- Results are estimates based only on the amounts and rates you enter.
- Returns are assumed to be constant and compounded monthly.
- A $0.00 contribution or a 0% return stays finite.
- The model stops at 100 years and does not invent an infinite wait.
- Scenarios are not saved, emailed or sent to analytics.
Frequently asked questions
What is FIRE?
FIRE is a common educational label for financial independence, retire early. In this worksheet it means the projected portfolio has reached a FIRE number you derived from spending and a withdrawal rate. It is a modeling label, not a life plan.
What is a FIRE number?
The FIRE number is annual spending divided by the withdrawal-rate decimal. With $60,000.00 of spending and 4%, the number is $1,500,000.00. The field does not look up a recommended nest egg.
What is the 4% rule?
The 4% figure is a common educational planning example used as this worksheet’s default withdrawal rate. It is a number you can change. The calculator does not say 4% is right for anyone.
How is financial independence estimated?
The worksheet grows the current portfolio and monthly contributions with monthly compounding, then looks for the first month when that balance is at least the FIRE number. Years needed is that month count divided by 12.
What if contributions are $0?
A $0.00 contribution is valid. Only the current portfolio grows at the rate you typed. If that growth still does not reach the FIRE number within 100 years, the result is not reached within the modeled horizon.
What if returns are 0%?
A 0% return is valid. The projection is the current portfolio plus monthly contributions times the number of months. There is no compound growth and no Infinity.
What if I already reached my FIRE number?
If the current portfolio is already at least the FIRE number, the result is “Already financially independent under these assumptions.” The calculator does not invent extra years.
Does this include taxes?
No. Taxes, withholdings and tax-advantaged account rules are not calculated. The amounts are whatever you type.
Does this include inflation?
No. The return, spending and withdrawal rate stay at the numbers you typed. Inflation is not applied automatically.
Does this include Social Security?
No. Social Security, pensions and other income streams are outside this worksheet. Only the portfolio, contribution, return, spending and withdrawal rate are used.
Does this guarantee retirement success?
No. Reaching a FIRE number in this model is a worksheet crossing. It does not guarantee that withdrawals will last, that returns will match the rate you typed or that anyone can retire.
What withdrawal rate should I use?
The calculator does not choose a rate. Enter the planning percentage you want to test. The default 4% is only an educational example.
How do higher contributions affect the estimate?
A larger monthly contribution usually reaches the FIRE number in fewer modeled months, if the other inputs stay the same. That is a worksheet result, not a recommendation to save more.
How do higher returns affect the estimate?
A higher expected return usually reaches the FIRE number in fewer modeled months, if the other inputs stay the same. The rate is not a forecast and not a guaranteed return.
Why is this only an estimate?
The model assumes a constant monthly rate, no taxes, no inflation adjustment and no market path. Real balances can be higher or lower. The 100-year cap also stops the search.
Is this financial advice?
No. It is an educational estimate from numbers you typed. It is not financial advice, retirement advice, a guaranteed independence date or a recommendation to invest.
Last reviewed August 25, 2026 (UTC).