{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"fire-number"},"result":{"entity_type":"calculator","id":"fire-number","calculator_id":"fire-number","canonical_url":"https://tttkmbb.com/finance/fire-number","name":"FIRE Number Calculator","title":"FIRE Number Calculator – Savings Needed for Financial Independence and Years to Reach It","category":"finance","category_name":"Finance","tool_name":"calculate_fire_number","featured_mcp_tool":false,"description":"Computes the portfolio needed to fund annual expenses at a safe withdrawal rate (the FIRE number, 25× expenses at 4 %), your progress towards it, and the years until current savings plus annual saving reach it at an assumed return.","use_when":"You want to know how much you need to retire early or become financially independent, and how many years of saving at your current rate it will take.","do_not_use_when":"You want to project a balance to a fixed retirement age (use retirement-savings) or test how long a balance lasts (use savings-withdrawal).","inputs":[{"name":"annual_expenses","label":"Annual expenses in retirement","type":"number","required":true,"max":1000000000,"exclusive_min":0,"description":"Yearly spending the portfolio must cover, in today's money.","example":40000},{"name":"withdrawal_rate_percent","label":"Safe withdrawal rate","type":"number","unit":"%","required":false,"default":4,"max":20,"exclusive_min":0,"description":"Percent of the portfolio withdrawn in the first year; 4 % is the Trinity-study rule, 3–3.5 % is more conservative for long retirements.","example":4},{"name":"current_savings","label":"Current investable savings","type":"number","required":false,"default":0,"min":0,"max":1000000000000,"description":"Amount already invested towards the goal.","example":100000},{"name":"annual_savings","label":"Annual savings","type":"number","required":false,"min":0,"max":1000000000,"description":"Amount saved and invested per year; takes precedence over annual_income × savings_rate_percent.","example":30000},{"name":"annual_income","label":"Annual income","type":"number","required":false,"min":0,"max":1000000000,"description":"Yearly income, used with savings_rate_percent when annual_savings is omitted.","example":100000},{"name":"savings_rate_percent","label":"Savings rate","type":"number","unit":"%","required":false,"min":0,"max":100,"description":"Percent of annual_income saved each year.","example":30},{"name":"annual_return_percent","label":"Annual return","type":"number","unit":"%","required":false,"default":7,"min":-50,"max":50,"description":"Expected annual return in percent; use a real (after-inflation) return since expenses are in today's money.","example":7},{"name":"current_age","label":"Current age","type":"number","unit":"years","required":false,"min":0,"max":100,"description":"Optional; enables the projected FI age.","example":30}],"outputs":[{"name":"fire_number","label":"FIRE number","type":"number","decimals":2,"description":"annual_expenses / (withdrawal_rate_percent / 100)."},{"name":"fire_multiple","label":"Multiple of expenses","type":"number","decimals":2,"description":"100 / withdrawal_rate_percent (25 at 4 %)."},{"name":"progress_percent","label":"Progress","type":"number","unit":"%","decimals":2,"description":"current_savings / fire_number × 100."},{"name":"remaining_to_save","label":"Remaining to reach the number","type":"number","decimals":2,"description":"max(0, fire_number − current_savings), before any growth."},{"name":"annual_savings_used","label":"Annual savings used","type":"number","decimals":2,"description":"annual_savings, or annual_income × savings_rate_percent / 100."},{"name":"years_to_fi","label":"Years to financial independence","type":"number","unit":"years","decimals":1,"description":"Years until savings plus growth reach the FIRE number (0 if already reached)."},{"name":"fi_age","label":"FI age","type":"number","unit":"years","decimals":1,"description":"current_age + years_to_fi (only when current_age is given)."}],"input_schema":{"type":"object","properties":{"annual_expenses":{"description":"Yearly spending the portfolio must cover, in today's money.","type":"number","maximum":1000000000,"exclusiveMinimum":0,"examples":[40000]},"withdrawal_rate_percent":{"description":"Percent of the portfolio withdrawn in the first year; 4 % is the Trinity-study rule, 3–3.5 % is more conservative for long retirements. Unit: %.","type":"number","maximum":20,"exclusiveMinimum":0,"default":4,"examples":[4],"x-unit":"%"},"current_savings":{"description":"Amount already invested towards the goal.","type":"number","minimum":0,"maximum":1000000000000,"default":0,"examples":[100000]},"annual_savings":{"description":"Amount saved and invested per year; takes precedence over annual_income × savings_rate_percent.","type":"number","minimum":0,"maximum":1000000000,"examples":[30000]},"annual_income":{"description":"Yearly income, used with savings_rate_percent when annual_savings is omitted.","type":"number","minimum":0,"maximum":1000000000,"examples":[100000]},"savings_rate_percent":{"description":"Percent of annual_income saved each year. Unit: %.","type":"number","minimum":0,"maximum":100,"examples":[30],"x-unit":"%"},"annual_return_percent":{"description":"Expected annual return in percent; use a real (after-inflation) return since expenses are in today's money. Unit: %.","type":"number","minimum":-50,"maximum":50,"default":7,"examples":[7],"x-unit":"%"},"current_age":{"description":"Optional; enables the projected FI age. Unit: years.","type":"number","minimum":0,"maximum":100,"examples":[30],"x-unit":"years"}},"additionalProperties":false,"required":["annual_expenses"]},"output_schema":{"type":"object","properties":{"fire_number":{"description":"annual_expenses / (withdrawal_rate_percent / 100).","type":"number"},"fire_multiple":{"description":"100 / withdrawal_rate_percent (25 at 4 %).","type":"number"},"progress_percent":{"description":"current_savings / fire_number × 100. Unit: %.","type":"number","x-unit":"%"},"remaining_to_save":{"description":"max(0, fire_number − current_savings), before any growth.","type":"number"},"annual_savings_used":{"description":"annual_savings, or annual_income × savings_rate_percent / 100.","type":"number"},"years_to_fi":{"description":"Years until savings plus growth reach the FIRE number (0 if already reached). Unit: years.","type":"number","x-unit":"years"},"fi_age":{"description":"current_age + years_to_fi (only when current_age is given). Unit: years.","type":"number","x-unit":"years"}}},"formula":"fire_number = annual_expenses / (withdrawal_rate_percent/100); with r = annual_return_percent/100, S = annual_savings (end of year) and C = current_savings: years_to_fi = ln((fire_number + S/r) / (C + S/r)) / ln(1 + r) (r ≠ 0), or (fire_number − C) / S when r = 0","method":"Annual compounding with savings added at the end of each year and constant returns. The 4 % rule comes from the Trinity study (Cooley, Hubbard & Walz 1998) for 30-year horizons with a 50–75 % stock allocation; longer retirements argue for a lower rate.","sources":[{"name":"Wikipedia – Trinity study (safe withdrawal rates)","url":"https://en.wikipedia.org/wiki/Trinity_study","type":"reference","retrieved_at":"2026-09-24"},{"name":"Wikipedia – FIRE movement","url":"https://en.wikipedia.org/wiki/FIRE_movement","type":"reference","retrieved_at":"2026-09-24"},{"name":"Investopedia – What Is the 4% Rule for Withdrawals in Retirement?","url":"https://www.investopedia.com/terms/f/four-percent-rule.asp","type":"reference","retrieved_at":"2026-09-24"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"40,000 expenses at 4 %, 100,000 saved, 30 % of 100,000 income, 7 %, age 30","inputs":{"annual_expenses":40000,"withdrawal_rate_percent":4,"current_savings":100000,"annual_income":100000,"savings_rate_percent":30,"annual_return_percent":7,"current_age":30},"expected":{"fire_number":1000000,"fire_multiple":25,"progress_percent":10,"remaining_to_save":900000,"annual_savings_used":30000,"years_to_fi":14.7,"fi_age":44.7},"url":"https://tttkmbb.com/api/v1/calculate/fire-number?annual_expenses=40000&withdrawal_rate_percent=4&current_savings=100000&annual_income=100000&savings_rate_percent=30&annual_return_percent=7&current_age=30"},{"name":"60,000 expenses at 3.5 %","inputs":{"annual_expenses":60000,"withdrawal_rate_percent":3.5},"expected":{"fire_number":1714285.71,"fire_multiple":28.57,"progress_percent":0},"url":"https://tttkmbb.com/api/v1/calculate/fire-number?annual_expenses=60000&withdrawal_rate_percent=3.5"}],"faq":[{"q":"Why 25 times expenses?","a":"Withdrawing 4 % of a portfolio each year means the portfolio must be 1 / 0.04 = 25 times the annual withdrawal. At 3.5 % it is 28.6×, at 3 % it is 33.3×."},{"q":"Should expenses include taxes?","a":"Yes. Withdrawals from pre-tax accounts are taxable, so annual_expenses should be the gross amount needed including income tax and health insurance."}],"tags":["fire number","financial independence","retire early","4 percent rule","years to retirement","savings rate"],"related":[{"calculator_id":"retirement-savings","reason":"Project the balance to a specific retirement age."},{"calculator_id":"savings-withdrawal","reason":"How long the portfolio lasts at a given withdrawal."},{"calculator_id":"rule-of-72","reason":"Doubling time at the assumed return."}],"links":{"html":"https://tttkmbb.com/finance/fire-number","markdown":"https://tttkmbb.com/finance/fire-number.md","json":"https://tttkmbb.com/finance/fire-number.json","api":"https://tttkmbb.com/api/v1/calculate/fire-number","schema":"https://tttkmbb.com/api/v1/calculators/fire-number","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T01:58:52Z","next_actions":[{"tool":"run_calculator","calculator_id":"fire-number","reason":"Run FIRE Number Calculator with the inputs above."}],"links":{"markdown":"https://tttkmbb.com/finance/fire-number.md"}}