What Your FIRE Number Is
Your FIRE number is the portfolio size you target so your investments can cover your planned spending after you stop working. People usually express it as a multiple of annual spending, then adjust for taxes, healthcare, and the way their withdrawal plan works in practice. For example, if you budget $48,000 per year and target a 4% withdrawal rate, a simple starting point is $1.2 million, but that number changes when you add taxes, insurance, and irregular expenses.
FIRE numbers are not predictions of market returns. They are planning targets built from assumptions you choose, then tested against risks like inflation and sequence-of-returns. A plan that looks fine on paper can fail if your spending estimate is too low, your tax assumptions are wrong, or your withdrawal timing forces you to sell investments during downturns.
Many calculators ask for your “annual expenses” and a “safe withdrawal rate,” then output a number. That output is only as trustworthy as the inputs, and it rarely matches reality unless you convert your spending into categories that behave differently over time.
Common Mistakes And Dependencies
People often treat “expenses” as a single number, then forget that some costs rise faster than others. Healthcare premiums, out-of-pocket costs, and long-term care exposure can behave differently from groceries or utilities. If your budget blends these together, you may understate the part that grows fastest.
Another frequent error is ignoring taxes. Withdrawals from a taxable brokerage account, traditional 401(k)/IRA accounts, and Roth accounts face different tax timing and tax rates. A FIRE number based on pre-tax spending can be too low if you plan to fund spending from accounts that trigger income tax.
Withdrawal mechanics matter too. A plan that assumes you can withdraw a fixed percentage each year may not match how you actually rebalance, how you handle required minimum distributions, or how you cover early retirement years before Medicare. The dependency chain is simple: your spending plan drives withdrawals, withdrawals drive taxes and account balances, and account balances drive how long the portfolio lasts.
Inflation is the other dependency people compress too aggressively. If you assume a single inflation rate for everything, you may miss that some categories rise faster. I once compared two budgets with the same total spending but different shares for healthcare and housing; the one with higher healthcare exposure needed a meaningfully larger buffer under the same withdrawal rule.
How To Find Your FIRE Number
1) Build A Spending Baseline
Start with a budget that reflects your real spending, not the spending you wish you had. Use at least 12 months of records, then separate costs into buckets: housing, food, transportation, insurance, healthcare, debt payments, and discretionary spending. If you track in a tool like Monarch Money or a spreadsheet, export totals by category and reconcile them against your bank statements; version 2024.1 of one budgeting app I used for testing had a reporting lag that made monthly totals look smoother than they were.
Decide whether your baseline is “spending you will still have” or “spending you will reduce.” If you plan to downsize housing, include the new housing cost, not the old one. If you plan to keep a car longer, include maintenance and insurance assumptions that match that timeline.
Then add irregular items. Many people forget annual property taxes, car repairs that don’t happen every month, and travel that happens once or twice a year. A practical approach is to compute an annual average for irregular costs from your last 2–3 years, then carry that average forward.
2) Choose A Withdrawal Assumption
Most FIRE discussions use a “safe withdrawal rate” as a planning shortcut. A common starting range is around 3% to 4% for long retirement horizons, but the right choice depends on your risk tolerance, portfolio mix, and whether you plan to adjust spending during downturns. If you plan to cut spending when markets fall, you can often support a higher initial withdrawal rate than a plan that never changes spending.
Instead of treating the withdrawal rate as a single truth, stress-test it. Run scenarios where returns are weak early in retirement, and where inflation is higher than expected. Even a simple spreadsheet can do this if you model a few sequences of returns and track whether the portfolio survives to your target horizon.
If you use an online calculator, record the date and the assumptions it uses. Some tools update their default inflation assumptions or tax handling, and the difference can move the FIRE number by tens of thousands of dollars.
3) Adjust For Taxes And Healthcare
Taxes often change the FIRE number more than people expect. Traditional IRA and 401(k) withdrawals are generally taxed as ordinary income in the U.S., while Roth withdrawals can be tax-free if qualified distribution rules are met. Taxable brokerage withdrawals include capital gains and dividends, and the tax rate depends on holding period and your income.
Healthcare is a separate line item with its own timing. Before Medicare eligibility, you may pay premiums through employer coverage, ACA marketplaces, or other routes, and you may also face out-of-pocket costs. After Medicare, premiums and cost-sharing still exist, and supplemental coverage can add cost. If you live in a state with higher premiums or have higher expected utilization, your healthcare budget should reflect that.
For a planning check, estimate your annual “after-tax spending need,” then back into a pre-tax withdrawal amount using a tax model or conservative approximations. If you do not want to build a full tax model, you can still bracket outcomes by using a low/medium/high tax scenario and seeing how much the FIRE number shifts.
4) Stress-Test With A Simple Plan
Once you have a spending baseline and a withdrawal assumption, test the plan against at least two risk dimensions: sequence-of-returns risk and inflation risk. Sequence-of-returns risk means poor market performance early in retirement can permanently reduce the portfolio’s ability to recover. Inflation risk means your spending rises faster than your portfolio’s real returns.
Use a timeline that matches your retirement start date. If you retire at 45, you have a long pre-Medicare period; if you retire at 60, the gap is shorter. Then decide how you will handle downturns: will you reduce discretionary spending, delay purchases, or shift withdrawals across account types?
One practical method is to create a “minimum spending” and a “target spending” plan. In a down market, you withdraw to cover minimum spending and defer discretionary spending. This approach can reduce the chance you sell investments at depressed prices, though it requires discipline and a clear rule set.
Case Examples For Real Budgets
Example 1: Early Retirement With ACA Coverage
Alex plans to retire at 48 and expects to use ACA marketplace coverage until Medicare eligibility. Alex’s baseline spending averages $55,000 per year, with healthcare averaging $9,000 annually during the pre-Medicare years. Alex holds most retirement savings in a traditional 401(k)/IRA and some in a taxable brokerage account.
Alex starts with a simple multiple approach using a 4% withdrawal rate, then adjusts upward for taxes because withdrawals from traditional accounts are taxed as ordinary income. Alex also models a higher healthcare budget for years with higher out-of-pocket spending. After stress-testing a weak early-retirement sequence, Alex finds the initial FIRE number estimate is too low and increases the target by adding a buffer for both taxes and healthcare volatility.
Example 2: Retiring Later With Roth Flexibility
Priya plans to retire at 62 and expects Medicare soon, with lower healthcare premiums than in the pre-Medicare years. Priya’s spending averages $70,000 per year, and the portfolio includes a meaningful Roth IRA balance plus taxable brokerage.
Priya uses a withdrawal plan that draws from taxable and Roth accounts first to manage taxable income, then shifts to traditional accounts later. This account-ordering changes the tax profile and can reduce the tax drag compared with a plan that withdraws only from traditional accounts. Priya still stress-tests inflation and sequence-of-returns, then sets a FIRE number that reflects after-tax spending needs rather than a pre-tax multiple.
FIRE Number Checklist And Table
| Input | What To Write Down | Common Error | How To Sanity-Check |
|---|---|---|---|
| Annual Spending | Category totals + irregular averages | Using one year only, skipping irregular costs | Compare last 12–36 months; reconcile with bank totals |
| Withdrawal Rule | Initial rate + spending flexibility | Assuming fixed spending during downturns | Run at least two return sequences; note failure points |
| Taxes | Account mix + tax brackets scenario | Treating pre-tax and after-tax as the same | Model low/medium/high tax outcomes; compare FIRE number range |
| Healthcare Timing | Pre-Medicare and Medicare costs separately | Using one average year for all years | Separate premiums from out-of-pocket; test higher out-of-pocket years |
Step-by-step checklist you can follow in a spreadsheet:
- Sum your last 12 months of spending by category, then replace any one-off expenses with a multi-year average.
- Separate healthcare into premiums and expected out-of-pocket costs, then project the pre-Medicare gap length.
- Pick a withdrawal approach: fixed percentage, or a rule that reduces spending when markets fall.
- Estimate taxes using your account mix and a conservative tax scenario, then convert your spending need to an after-tax basis.
- Stress-test at least two weak early-retirement sequences and one higher-inflation scenario.
- Set your FIRE number as the portfolio size that survives your chosen horizon under those scenarios, then add a buffer if your data is uncertain.
Common Mistakes That Undermine Trust
One mistake is using a single “safe withdrawal rate” without checking whether your plan includes spending flexibility. If you assume a fixed withdrawal rate but also plan to cut spending during downturns, you are mixing two different models. The result can look precise while hiding a major assumption.
Another mistake is ignoring account order. If you have Roth, taxable, and traditional accounts, the sequence of withdrawals affects taxable income and capital gains realization. A FIRE number built from a simplistic “all withdrawals are taxed the same” assumption can misstate the target.
People also underestimate how much uncertainty exists in healthcare. Premiums and out-of-pocket costs vary by plan choice, age, and utilization. If you only budget premiums and ignore out-of-pocket spending, your plan can fail in years with higher medical use.
Finally, some calculators treat inflation and returns as smooth averages. Real markets move in bursts, and your plan depends on what happens early. If your stress test uses only average returns, you may miss the scenario that matters most for longevity.
FAQ
What does “FIRE number” mean in practice?
It is the portfolio size you target so investment withdrawals can cover your planned spending after you stop working, after accounting for taxes and healthcare costs.
Should my FIRE number use pre-tax or after-tax spending?
Use after-tax spending needs when you plan withdrawals across different account types, because taxes differ between taxable brokerage, traditional retirement accounts, and Roth accounts.
How do I estimate healthcare costs for FIRE planning?
Separate pre-Medicare premiums and out-of-pocket costs from Medicare-era premiums and cost-sharing, then test a higher out-of-pocket year to reflect utilization variation.
What withdrawal rate should I use?
Start with a common planning range, then stress-test it with your spending flexibility and portfolio mix; the “right” rate depends on whether you reduce spending during downturns.
How often should I recalculate my FIRE number?
Revisit it when your spending baseline changes meaningfully, when tax rules or account balances shift, or at least annually to reflect new data and updated budgets.
Author's Insight
A FIRE number is a planning construct, not a guarantee. The most defensible versions translate your budget into after-tax spending needs, separate healthcare timing, and test sequence-of-returns risk rather than relying on average returns. When people get different FIRE numbers from the same calculator, the differences usually come from taxes, healthcare assumptions, and withdrawal rules, not from the math itself. A careful workflow—budget categories, account mix, and stress tests—turns a vague target into a decision tool you can revise as facts change.
Key Takeaways
- Your FIRE number is the portfolio size needed to fund your planned spending after work, using assumptions you can explain and test.
- Spending estimates should include irregular costs and separate healthcare from other categories that inflate differently.
- Taxes and account order often move the FIRE number more than a small change in the withdrawal rate.
- Stress-test weak early-retirement returns and higher inflation, then decide how you will respond during downturns.
- Recalculate when your budget, account mix, or healthcare timeline changes, because the inputs drive the output.
