Start with today’s dollars
How to use this FIRE calculator
- 1Enter current invested assets and contributions.
Use individual or household totals consistently throughout the form.
- 2Enter spending and recurring income from the FIRE date.
The portfolio funds only the portion of spending not covered by the recurring income you enter.
- 3Choose a target age, return, and withdrawal rate.
Compare the current path, target-age contribution estimate, and withdrawal-rate table rather than relying on one number alone.
What your results mean
Your FIRE number is based on the entered annual spending, recurring annual income, and selected withdrawal rate. Current progress compares invested assets with that target today.
The estimated FIRE age is the first modeled month in which real projected assets reach the target. The target-age contribution result estimates the additional monthly amount needed from now, while keeping the other assumptions unchanged.
If recurring income covers all entered spending, the FIRE number is $0. This calculator does not test whether that income is guaranteed, inflation-adjusted, taxable, or available for life.
Rule of thumb plus accumulation
FIRE number formula and calculation method
- Portfolio-funded annual spending = the greater of expected annual spending − recurring annual income or $0.
- FIRE number = portfolio-funded annual spending ÷ selected withdrawal rate.
- Real annual return =
((1 + net nominal return) / (1 + inflation)) − 1. - Monthly real return =
(1 + real annual return)^(1/12) − 1.
The engine applies monthly real growth and then end-of-month contributions by default. It changes real contributions at year boundaries, finds the first month in which assets meet the target, and does not project beyond age 100.
A bounded solver estimates the extra monthly contribution for the target age. It verifies the ending value against its tolerance and returns a supported-range message instead of inventing an exact answer when it cannot converge.
Worked example
With $60,000 of annual portfolio-funded spending and a 4% withdrawal rate, the FIRE number is $60,000 ÷ 0.04 = $1,500,000. A 4% rate is the same as a 25× spending multiplier.
Assumptions and limitations
- The model is deterministic. It uses constant return, fee, inflation, and real contribution-growth assumptions instead of simulating different market paths.
- The withdrawal-rate comparison is a rule-of-thumb scenario. It does not guarantee that a portfolio will last through an unknown retirement length.
- Taxes, investment allocation, sequence-of-returns risk, changing spending, insurance before Medicare, health costs, long-term care, and flexible withdrawals are not modeled.
- The recurring-income field assumes the income starts on the FIRE date and continues each year. Use the retirement calculator when income begins later or needs separate timing.
- Invested assets can include 401(k) and IRA balances, but this page does not model access rules, taxes, or early-withdrawal consequences.
Common questions
Frequently asked questions
What is a FIRE number?
It is an estimated invested-asset target based on annual spending not covered by the entered recurring income and a selected withdrawal rate. It is a planning rule of thumb, not a guarantee.
Why is the 4% rule the same as multiplying by 25?
Dividing by 4%, or 0.04, is mathematically the same as multiplying by 25. For example, $60,000 divided by 0.04 equals $1.5 million.
Should early retirees use less than 4%?
A longer withdrawal horizon can make a lower rate worth testing, but no single percentage suits every plan. Compare the five scenarios here and use a fuller retirement model before making a decision.
Does the FIRE number include inflation?
The FIRE number and accumulation path are shown in today’s dollars. The calculator converts the entered nominal return and inflation into a real return so the target and projected assets remain comparable.
Can couples use this FIRE calculator?
Yes. Enter combined assets, contributions, spending, and recurring income consistently. The calculator treats them as household totals and does not model separate tax or account histories.
Should 401(k) and Roth IRA balances count as invested assets?
They can count toward a broad invested-asset total, but account access, taxes, qualified-distribution rules, and early-withdrawal consequences matter. Use the account-specific calculators and consider professional guidance.
What are Lean FIRE, Fat FIRE, Coast FIRE, and Barista FIRE?
Lean FIRE generally means planning around lower spending, while Fat FIRE uses a higher spending target. Coast FIRE focuses on having enough invested that future growth may fund a later retirement without new contributions. Barista FIRE combines invested assets with continued work or other income. This calculator models one spending, income, and contribution scenario rather than separate labels.
What should I calculate after finding my FIRE number?
Test the income goal and lifespan in the retirement calculator, then model current workplace and IRA contributions with the 401(k) and Roth IRA calculators.
Sources and research context
- Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable (accessed July 27, 2026)
- Early-retirement withdrawal-rate analysis (accessed July 27, 2026)
- Morningstar retirement-income research (accessed July 27, 2026)