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FIRE Calculator

See how saving and spending shape your FIRE target and timeline.

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FIRE Calculator

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How to use

Using this calculator

Formula 1.0 · Updated Oct 27, 2026

Planning estimate. No independent professional review is claimed. Check the method and sources before making a financial decision.

Getting started

Test a financial-independence scenario using your spending, annual savings, entered net worth, nominal return and inflation assumptions. The default portfolio target divides annual portfolio-funded spending by a 4% initial-withdrawal assumption. It is a planning benchmark, not a retirement approval or a promised safe outcome.

The timeline uses constant returns in today’s dollars. It does not simulate market sequences, account-specific withdrawal restrictions, taxes, fees not included in your return, or a complete Social Security claiming strategy. Enter only assets you can reasonably make available to fund the modeled spending.

Reading your results

Years to FI and FI age are scenario outputs based on your entered net worth, annual savings, spending target, return and inflation. A change in savings or spending can move the timeline; starting assets, withdrawal assumptions and investment returns also matter.

Compare one change at a time and review the 50-year projection alongside its assumptions. A target not reached within the horizon is not proof it can never be reached. Account access, taxes and healthcare must be planned separately.

Method & formulas

The historical 4% initial-withdrawal guideline predates the 1998 Trinity study: William Bengen published his historical analysis in 1994, and Cooley, Hubbard and Walz studied withdrawal outcomes in 1998. Their historical portfolio tests do not guarantee a future result or identify one suitable withdrawal rate for everyone.

  1. Portfolio target equals the modeled annual portfolio-funded spending divided by 0.04. FIRE variants change the assumed spending; they are scenarios, not classifications of financial health.

  2. Real growth uses (1 + nominal return) ÷ (1 + inflation) − 1. At 7% nominal return and 3% inflation this is about 3.8835%, rather than exactly 4%. The annual savings amount is treated as an end-of-year contribution in today’s dollars.

  3. Timeline projects the entered net worth and contributions for up to 50 years. A target not reached within that horizon is labeled as not reached. The model does not determine whether retirement-account assets can be withdrawn without tax or penalties.

  4. Social Security is an optional simplified annual offset only in scenarios whose modeled independence age is at least 62. It is not an eligibility check or a benefit-by-benefit bridge calculation. Test a zero-benefit case and obtain an SSA estimate for your actual claiming age.

Assumptions & limitations

Scope

  • Assumes a constant rate of return; real markets are volatile year to year
  • Social Security is modeled as a simple annual offset beginning at an eligible projected FIRE age, not as a detailed claiming strategy
  • A projection, not a guarantee: revisit your numbers regularly

Important notes

  • This calculator is for planning and educational purposes. It does not constitute financial, tax, or investment advice.
  • Update your numbers at least once a year, or after any major income, expense, or life change.

Before you act

  • Investment returns are never guaranteed and can vary significantly from the expected return you enter.
  • A market downturn shortly before or after reaching your FIRE number carries outsized risk (sequence-of-returns risk) -- consider a more conservative withdrawal rate than 4% if this concerns you.
  • A target and timeline are scenario outputs. Taxes, withdrawal access, healthcare, market sequences and the availability of entered assets can change an actual retirement plan.

Related Calculators

Retirement Savings CalculatorProject retirement savings with monthly contributions and a constant-return scenario, then compare the result with a 4% first-year withdrawal planning target.Net Worth CalculatorBuild a point-in-time personal balance sheet by totaling assets and liabilities, with category summaries and an asset-to-debt ratio.Compound Interest CalculatorSee how deposits, time and returns shape your savings.

FAQs

Common questions (8)
What is FIRE?

FIRE stands for Financial Independence, Retire Early. It is a strategy of saving and investing enough that your portfolio can support your living expenses without depending on employment income.

What is the 4% rule?

The 4% rule is a retirement-planning guideline that starts annual withdrawals at 4% of a diversified portfolio, then adjusts that dollar amount for inflation. It is a planning estimate, not a guarantee.

What is Lean FIRE?

Lean FIRE targets financial independence with a deliberately low-cost lifestyle. This calculator models Lean FIRE at 70% of your current annual spending.

How much do I need to retire at 40?

Start with the annual spending you expect at age 40 and multiply it by 25 under the 4% rule. Then account for healthcare, taxes, a longer retirement horizon, and a safety margin appropriate to your circumstances.

What savings rate do I need for FIRE?

There is no universal rate, but a higher savings rate can shorten the timeline substantially. The calculator uses your actual take-home income, monthly savings, current assets, debts, and return assumptions to estimate your path.

What are Regular, Fat, and Barista FIRE?

Regular FIRE aims to maintain your current lifestyle, Fat FIRE plans for higher spending, and Barista FIRE combines a smaller portfolio with part-time income. This calculator lets you compare all four modes.

Does this FIRE calculator include Social Security?

Yes. You can add an estimated monthly benefit. The calculator applies it only when your projected financial-independence age is 62 or later.

How accurate is this FIRE calculator?

It is a planning model based on constant real returns and the inputs you provide. Markets, inflation, taxes, benefits, and spending vary, so review multiple scenarios and update your plan regularly.

Sources

Sources (3)
  1. Bengen (1994): Determining Withdrawal Rates Using Historical Data (publisher access may require membership)
  2. Cooley, Hubbard and Walz (1998): Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable
  3. Social Security: Retirement benefit planning