Turn your retirement spending into a target portfolio
FIRE Number Calculator
Your FIRE number is the investment portfolio you may need before work becomes optional. Use this FIRE number calculator to test spending, retirement income, and withdrawal-rate assumptions before you build a longer retirement timeline.
fire number calculator
What your FIRE number tells you
The FIRE number is a target, not a finish line that explains every risk. A number based on $45,000 of annual spending is very different from one based on $80,000. Housing, healthcare, taxes, dependents, travel, and one-time purchases deserve their own line in your planning assumptions.
The simplified formula is annual retirement spending minus reliable retirement income, divided by the selected withdrawal rate. This tool also shows how your current portfolio and annual contributions may move you toward the target. It does not model every tax rule, fee, or market path.
How to use this tool
- 1.Enter your current age, portfolio, income, spending, and annual investing.
- 2.Adjust return, inflation, withdrawal rate, and reliable retirement income.
- 3.Run the estimate, review the target and age, then download your result.
Example: why the withdrawal rate matters
A $50,000 annual spending gap produces a $1,250,000 target at a 4% withdrawal rate before other adjustments. Lowering the withdrawal rate increases the required portfolio, while adding reliable retirement income reduces the gap. Use the calculator to compare these cases instead of treating one rule as universal.
Inputs
Age, spending, investments, contributions, return, inflation, and withdrawal rate.
Outputs
FIRE number, estimated age, savings rate, Coast FIRE number, and target-age balance.
Download
Export your inputs and result summary as a CSV file for review or sharing.
Decision guide
How to read your fire number calculator result
The calculation begins with a spending gap. Subtract reliable retirement income from the annual amount your future lifestyle may require, then connect that gap to a withdrawal rate. This creates the target portfolio commonly called a FIRE number. The target is useful because it makes trade-offs visible: lower spending reduces the gap, dependable income reduces the amount the portfolio must supply, and a more conservative withdrawal rate increases the margin. None of these choices is automatically right; the point is to see the consequence of each choice.
Run more than one scenario before making a major decision. A base case can use your best current estimate. A stress case can use higher healthcare or housing costs, lower real returns, slower contributions, or less retirement income. A flexibility case can add part-time work, a later retirement age, or a temporary spending reduction. When several reasonable cases point to a similar range, the result becomes a useful planning boundary. When a small input change moves the answer dramatically, that input deserves more research.
Base case
Use your best current estimate for spending, investing, income, inflation, and real return. Update it when household numbers change.
Stress case
Lower the return assumption, raise spending, or reduce future income to test a less convenient market or employment path.
Flexibility case
Test saving longer, working part-time, reducing spending temporarily, or delaying a major purchase.
Before you decide
Questions to ask before relying on a fire number calculator
Spending deserves more attention than a single annual total. Check housing, healthcare, insurance, taxes, transportation, travel, family support, repairs, subscriptions, and irregular purchases. Decide whether a cost will disappear, continue, or grow after full-time work ends. Treat optional income differently from income you can reasonably rely on. A plan that only works when every bonus, side job, or benefit arrives on time may need a larger cash reserve or a more flexible withdrawal approach.
- Spending: Have you included healthcare, taxes, housing repairs, transportation, family support, and irregular purchases?
- Income: Would the plan still work if part-time work, a bonus, a pension, or a benefit were smaller or delayed?
- Access: Can you reach the accounts you need at the age your plan assumes, after considering taxes and withdrawal rules?
- Flexibility: Which expenses could be paused or reduced during a long market decline without damaging your quality of life?
Keep it current
When to rerun your fire number calculator
Account location can change how a portfolio is used. Taxable investments, traditional retirement accounts, Roth accounts, and cash may have different access rules, taxes, and timing considerations. Advanced mode makes the starting balance easier to audit, but it does not calculate a personal tax strategy. Use the account breakdown to ask better questions: which assets are available in the first years, which withdrawals may create taxable income, and how much liquidity is needed before a longer-term account can be used?
Time is another major input. A longer runway gives contributions and compounding more opportunity, while a shorter runway makes the result more sensitive to savings, spending, and market returns. The projected FIRE age is therefore a scenario output, not a promise that work must end on one exact birthday. Compare the result with a target age and with a range of ages. A plan can be successful even when the date changes, if it gives you more control over the next decision.
Review the result after meaningful changes in income, expenses, savings, investments, household needs, or retirement timing. A regular review once or twice a year can replace old assumptions with actual results. Save dated CSV exports so you can see whether the target moved because of your behavior, the market, or the assumptions. Keeping the earlier version is valuable: it shows progress and prevents a new optimistic assumption from hiding a real change in risk.
Use the calculator as an educational planning record, not as a substitute for professional advice. If the decision involves taxes, insurance, estate planning, concentrated investments, debt, or a large irreversible purchase, verify the relevant rules with current official information and a qualified professional. The strongest output is not the earliest possible date. It is a scenario you understand, a margin you can explain, and a next step you can actually take.
The FIRE number formula
The simplified formula is annual retirement spending minus reliable retirement income, divided by the selected withdrawal rate. This tool also shows how your current portfolio and annual contributions may move you toward the target. It does not model every tax rule, fee, or market path.
1. Spending gap
Annual retirement spending minus reliable retirement income.
2. FIRE number
Spending gap divided by the withdrawal rate you choose.
3. Timeline
Current assets and annual investing are projected using a return adjusted for inflation.
What this calculator includes
- • Current investments and annual contributions.
- • Inflation-adjusted returns and a configurable withdrawal rate.
- • Retirement income from part-time work, pensions, or benefits.
- • Coast FIRE number and estimated Coast FIRE age.
- • Advanced account breakdown for taxable, traditional, Roth, and cash balances.
Important limitations
A FIRE number can change when your lifestyle changes. Review the target annually and test a higher-spending scenario for healthcare, housing repairs, family support, and other costs that are easy to omit from a first estimate.
The estimate is educational. It does not predict markets, calculate personal taxes, or guarantee that a retirement date will be achievable.
Frequently asked questions
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