FIRE calculator FAQs

Start with the question you want to answer. Use the FIRE Number Calculator for a spending-based portfolio target, Coast FIRE for the amount needed today to grow toward a later retirement target, or Barista FIRE for work income that supplements withdrawals for a limited period. Use Fat FIRE or Lean FIRE to build a budget and test a savings timeline. You can use several tools for different stages of the same plan.

The Coast model leaves investments untouched until the retirement age you enter; other resources must cover living costs in the meantime. The Barista model starts a work-income period now and withdraws any gap between spending and take-home income from investments each month. When that income ends, it requires a full spending-based retirement target. It makes no additional contributions and does not save work income above expenses. See the two-stage Barista calculation.

They use the same accumulation calculation, with different budget labels and editable examples. Fat FIRE separates core costs, lifestyle spending, and an annual reserve; Lean FIRE separates essentials, flexible spending, and an annual reserve. Both divide the total annual budget by the withdrawal rate, then project current assets and monthly contributions toward that target. Neither label has an official dollar threshold. Build the budget around your own costs rather than treating the defaults as a recommendation.

Use investments allocated to the expenses this plan is meant to fund. Exclude emergency savings and money earmarked for other purchases. Do not count home equity unless your separate plan converts it into usable investment funds; these tools do not model a home sale. Account access also matters: a projected balance does not establish when you can withdraw from a retirement account. Barista FIRE requires accessible resources for withdrawals starting now.

Yes, include the costs that your portfolio must fund. The tools do not calculate tax brackets, insurance premiums, or investment fees. Enter annual spending in today’s USD; multiply a monthly budget by 12 and add annual costs once. In Fat and Lean FIRE, an annual reserve is a recurring allowance for uneven expenses, not a separate pot of emergency savings. Avoid entering the same cost in both the core budget and the reserve.

Use the Barista income field for take-home work income that begins now and lasts for the whole number of years you enter. The FIRE Number income field is only for usable income available throughout the retirement period you are modeling. A future pension or Social Security benefit cannot simply be subtracted from spending that starts today; these tools do not calculate benefit eligibility, start dates, or changing payments. Coast, Fat, and Lean have no separate income schedule. Model timing separately before relying on an income-adjusted target.

All five tools use today’s USD. Coast, Barista, Fat, and Lean convert nominal annual return into a real return using (1 + nominal return) ÷ (1 + inflation) − 1. With 7% nominal return and 3% inflation, that is about 3.88%, not exactly 4%. Enter spending in today’s purchasing power rather than inflating it first. FIRE Number has no growth forecast or inflation field; its spending and continuing income must use the same purchasing-power basis. See the formula explanation.

No. Coast, Fat, and Lean model contributions at each month’s end with constant purchasing power. If you enter $1,000 a month, future nominal contributions would need to rise with the inflation assumption to maintain that purchasing power. A savings plan that stays at exactly $1,000 nominal each month would follow a different path. Barista makes withdrawals during its income period, and FIRE Number has no contribution timeline. See contribution timing.

The targets fund different cash flows. For $40,000 a year at a 4% withdrawal rate with no other income, the full spending target is $1,000,000. Coast discounts that future target to today. Fat and Lean show the full budget target and a savings path toward it. FIRE Number shows the target without a timeline. Barista includes withdrawals during the work-income period plus the full target when work income ends. Compare the target’s meaning, income duration, ages, return assumptions, and total budget before comparing the dollar amounts.

No. These are deterministic estimates under the inputs you choose. They do not simulate market volatility, sequence of returns, tax rules, fees, or withdrawals throughout your later retirement. A withdrawal rate is an assumption, not a guaranteed outcome; an investment return is a growth assumption, not a promised withdrawal rate. Meeting the Coast target also leaves current living costs to be funded separately. Compare multiple scenarios and read the withdrawal-rate context and model limits.

In Coast, Fat, or Lean, it means the modeled balance does not meet that tool’s target within the age range you entered. It does not mean the target is impossible under every plan. Compare a different contribution, budget, age, or return assumption and inspect the projected balance at your chosen age. Higher assumed returns can improve the arithmetic without making the plan more reliable. FIRE Number does not predict an age; Barista instead reports funding and possible depletion during its income period.

All five calculators are free and require no account. Financial values are calculated in your browser and are not saved between reloads. Our calculator code does not upload inputs or results to a server or add them to analytics. The production site uses Google Analytics for website visits. We do not send custom calculation or validation events; Google’s automatic measurement may include page interactions. Hosting still processes ordinary request data. Read the privacy details, and use a hypothetical example when reporting a calculation issue.