What this calculator includes
- All spending, balances and contributions use today’s purchasing power.
- Nominal effective annual return, separate annual asset fee and exact inflation conversion.
- Explicit zero, negative-growth, already-reached and out-of-range results.
- Accessible growth chart, annual checkpoints and complete monthly CSV.
- Private in-tab inputs, currency labels without FX conversion, reset and print.
How to use the FIRE retirement calculator
- Enter your current age and invested retirement assets, excluding amounts you cannot appropriately commit to this model.
- Estimate annual retirement spending the portfolio itself must fund, in today’s money. Include retirement taxes and healthcare you expect the portfolio to pay; do not subtract future benefits without checking dates and eligibility separately.
- Enter a fixed-real monthly contribution. This contribution maintains purchasing power, so the actual nominal deposit would rise with inflation.
- Choose nominal effective annual return, fee, inflation and withdrawal assumptions. The 4% example is a selectable scenario, not a guaranteed safe rate.
- Set a maximum projection age. Optionally enter a target age to calculate its required savings separately. Review slower/faster growth scenarios, then save the full schedule.
FIRE number formula and inflation-adjusted growth
F = annual portfolio-funded spending ÷ withdrawal fraction. With a 4% fraction, F is 25 times the entered annual spending. A different chosen withdrawal rate changes the target; the tool does not choose a suitable rate for your retirement horizon.
Net nominal annual factor = (1 + return) × (1 − fee). Real annual factor = net nominal factor ÷ (1 + inflation). Effective monthly factor = real annual factor^(1/12). Monthly balance = prior balance × monthly factor + end-month contribution. All rate inputs are percentages converted to decimal fractions in these formulas.
The engine checks each whole month until the target is first met or the chosen maximum projection age is reached. It does not interpolate a fractional month and label it a verified retirement date. A target not reached inside this horizon is not a claim that it can never be reached.
Worked FIRE number and savings examples
| Scenario | Inputs | Result |
|---|---|---|
| Portfolio target | 40,000 annual spending ÷ 4% | 1,000,000 |
| Lower withdrawal assumption | 40,000 ÷ 3% | 1,333,333.33 |
| Higher withdrawal assumption | 40,000 ÷ 5% | 800,000 |
| Zero-growth accumulation | 100,000 start + 1,000/month toward 200,000 | First target month 100 |
The 3%, 4% and 5% cases are arithmetic comparisons, not recommendations or success probabilities. Longer retirement periods, uncertain returns and less flexible spending can change the withdrawal plan that needs evaluation.
Default example: age35, assets150,000, 1,500 monthly in today’s money, spending40,000, 7% nominal return, 0.25% fee, 2.5% inflation and 4% withdrawal. Real annual growth is about4.1293%; the modeled first target month is264, at age57. These are original assumptions, not observed household results.
Work backward from a chosen target age
For n remaining months and effective monthly rate i, let A = [(1+i)^n − 1] ÷ i; at i=0 use n. Required monthly contribution = max(0, [F − current assets(1+i)^n] ÷ A). The displayed required amount rounds upward to cents so the minimum is not understated.
At the current age there is no time to add a recurring deposit. If assets are below target, the result states that an additional lump sum is required rather than returning an infinite monthly payment. If existing assets alone cover the selected-age target under assumptions, required further savings are zero.
The selected-age projection assumes deposits continue to that age. The main table stops at first target attainment or the projection horizon. Neither schedule models retirement withdrawals after you stop contributing.
FIRE versus Coast FIRE: two different milestones
FIRE accumulation asks when ongoing assets and contributions could meet the full spending-based portfolio target. Coast FIRE asks whether assets already invested could grow to that future target without further retirement deposits. A Coast threshold can be met while current assets remain far below the full FIRE number.
Use the separate Coast FIRE calculator when considering a no-more-contributions scenario. Reaching its threshold still leaves current living expenses to fund through work or another source.
A target age is not a safe retirement verdict
A constant growth path hides sequence risk: the order of gains and losses can materially affect a portfolio while withdrawals occur. This tool does not backtest historical series, run Monte Carlo paths or test how long withdrawals last. A result that says target reached is only an accumulation threshold under entered assumptions.
Plan retirement taxes, healthcare, housing changes, emergencies, dependants and access to different accounts separately. Retirement-account restrictions and future pension or Social Security dates are not inferred from your age. Do not treat all net worth, including a home you plan to occupy, as an automatically spendable portfolio.
Compare assumptions and revisit records. The three rate scenarios change growth assumptions only; they are not confidence bands or probabilities. The separate withdrawal-rate table changes the target only; it does not validate the chosen rate.
Assumptions and limits
This is a deterministic accumulation model, not a drawdown simulation, market forecast, success probability or decision that you can retire. Enter nominal effective annual return before the fee entered here. The assumed annual asset fee reduces the post-return annual value: (1+return)×(1-fee). Inflation is then removed by division, not subtraction. If your rate already includes the same fee, enter zero extra fee to avoid counting it twice. Fixed-real monthly contributions are paid at month-end; their nominal amounts would need to rise with inflation. Portfolio-funded annual spending must include applicable retirement taxes, healthcare and other expenses you intend the portfolio to cover. Benefits, pensions, access restrictions, individual tax rules, changing spending and market-return sequences are not calculated. Home equity and emergency cash are not automatically counted as invested retirement assets. Currency labels do not convert values. Current inputs are memory-only and reset on reload. Bounds are support limits, not recommended return/withdrawal ranges.
Frequently asked questions
What does FIRE stand for?
Financial Independence, Retire Early. This calculator estimates a spending-based portfolio target and accumulation timing; it does not decide whether retiring is appropriate.
How is my FIRE number calculated?
Divide annual retirement spending that your portfolio must fund by your selected withdrawal fraction. At 40,000 and 4%, the number is 1,000,000 in today’s money.
Does reaching the FIRE number guarantee my money lasts?
No. This model does not simulate retirement drawdown, changing returns, taxes or lifespan. A threshold calculation cannot certify withdrawal sustainability.
Are monthly contributions nominal or inflation-adjusted?
They are fixed in today’s purchasing power. Maintaining them would require increasing nominal deposits with inflation; Future Value instead models fixed nominal deposits.
Why is my target not reached?
The chosen assets, contribution and real growth did not meet the threshold within your selected projection age. Review assumptions; a negative real rate can reduce progress.
Can I leave target age blank?
Yes. The main accumulation projection still runs. The separate required-monthly-savings result asks you to choose a target age.
Is Coast FIRE the same calculation?
No. Coast FIRE discounts a future full target back to the invested amount needed today with zero further contributions. This FIRE tool includes continued monthly saving.
Method references
Check the zero-further-contribution Coast milestone
Coast FIRE discounts a future retirement target to the invested balance needed today. It does not fund today’s living costs.
Open Coast FIRE calculatorExplore Pro plan comparisonsPublished by MyBreakeven. Method and examples checked . Business calculation methodology · Check scope and corrections.