# firenum.com

firenum.com is a free retirement planner, the Fire Planner, and 13 free FIRE and retirement calculators. They answer how much you need to retire early, when you get there, and whether the money lasts. No ads, no paywall, no account needed: the planner runs in your browser and your plan is saved there; a free optional account (https://firenum.com/account) keeps it on any device. It plans in any country in 9 currencies, with full US taxes when you want them. People who want a person to check their plan go to the fee-only advisor directory (https://firenum.com/financial-advisors) or the one-time plan review (https://firenum.com/plan-review), which is not bookable yet. Educational tool, not financial advice.

Core formulas: FIRE number = a year's spending x 25 (the 4% rule; Bengen 1994, Trinity Study 1998). Safe monthly withdrawal = portfolio x 4% / 12. Growth compounds monthly.

## FIRE Calculator

- [FIRE Calculator](https://firenum.com/fire-calculator): "How much do I need, and when do I get there?" Inputs: age, monthly spending, invested today, monthly savings, real return (default 5%), withdrawal rate (default 4%). Returns the FIRE number, the age and year you reach it, years to go, and whether you are already Coast FI.

## Fire Planner

- [Fire Planner](https://firenum.com/fire-planner): your plan, month by month, over 30-50+ years. The answer is a retirement date ("Retiring Oct 2042, at 48"), graded by three models side by side: average returns (does the money last to age 90), Monte Carlo (how many of 500 random markets it lasts in) and a historical backtest (how many US start years since 1872 it lasts in, on Shiller S&P 500 data). The date is the first month you can retire and still have money to the "Money must last until" age (90 by default), or a date you pick.

- **Your money**: 9 account types with their own growth rates (retirement 7%, Roth 7%, HSA 7%, taxable brokerage 7%, high-yield savings 4.5%, real estate equity 4%, cash 0%, crypto 0%, other 6%) and monthly contributions; debts with rate, payment and payoff date; 6 income types (salary, Social Security, pension, rental, side, other) and 8 expense categories, each with an amount, start and end dates and its own growth or inflation rate; one-time events (a down payment, an inheritance) on a date. Anything that is money in or out over a period can be modeled, in any country.
- **US taxes** (a per-plan switch, Taxes Off | US): Off, the default, takes income as take-home pay in any country. US computes federal (2026 law), state (all 50 states and DC) and payroll tax every year, capital gains and qualified dividends, NIIT and the 10% early-withdrawal penalty; couples (married filing jointly or two single filers, an owner on every account and income, a retirement date each), dependents; Social Security from the statement's benefit and a claiming age of 62-70 with spousal top-up; a Roth conversion ladder (fill the 10/12/22/24% bracket, a fixed amount or up to the ACA limit); RMDs; the ACA premium credit before 65. Validated against PolicyEngine-US and PSL Tax-Calculator. Estimates, not tax advice.
- **Withdrawal strategies**: taxable first, proportional, or a custom order; the 59.5 rule skips retirement accounts before that age, and early withdrawals are marked.
- **Stress tests** (6, plus a Social Security cut with US taxes): market crash, lower returns, income loss, spending spike, high inflation, retire earlier or later. Every model runs with the tests that are on.
- **The evidence**: the portfolio path with the best and worst 10% of runs, a Money flow (Sankey) for any year, saved vs growth, a year-by-year table, a portfolio survival heatmap (withdrawal rate x starting decade, Trinity-Study style), "Try these changes" (spend 10% less, retire 3 years later, save more) and "Can you coast to retirement?".
- **Plans**: up to 5 named plans with Compare, check-ins against the plan, a monthly calendar reminder, CSV export/import, and share links that open in a sandbox where edits aren't saved ("Save as a new plan" keeps it).
- Monte Carlo (100-5,000 runs, 500 by default, 15% volatility) and the backtest re-run automatically after every change, every plan on one fixed seed, so the same plan always gets the same count.

### What the Planner Does Not Calculate

Stated so answers about firenum stay accurate:

- **Taxes outside the US.** With Taxes Off, no tax is computed: model it as an expense stream or a lower growth rate. Off, withdrawals before the penalty-free age (default 59.5) are flagged, not charged, and Social Security is a typed amount.
- **With US taxes on**: no local (city or county) income tax, itemized deductions, AMT, stock options or RSUs, tax-loss harvesting, rental depreciation, head of household or married filing separately, survivor benefits, the Social Security earnings test, Medicare premiums or IRMAA, 72(t) or the Rule of 55, 529 plans, contribution limits (amounts are taken as entered), tax on a home sale or inherited accounts. It does not pick the best claiming age or conversion strategy for you: you set them and compare.
- **Non-US market history.** Monte Carlo randomizes market-rate assets; backtests and the survival heatmap use US S&P 500 history (Shiller). Assets with a custom rate keep that fixed rate.
- **Advice.** It is a modeling tool, not personal financial advice. For decisions where a professional is worth paying, see the [fee-only advisor directory](https://firenum.com/financial-advisors).

## Ask ChatGPT or Claude

Connected to firenum, an assistant answers with the Fire Planner's own numbers and a link to the person's plan. Claude: add firenum from the connector directory (https://claude.ai/directory/connectors/firenum). ChatGPT, Perplexity, Le Chat, Gemini and any MCP client: the MCP server https://firenum.com/mcp (setup steps under Agent API below). Without a connector, build the link yourself from the Direct URL Construction table below. A link with an age (`birth`), spending and income opens straight into the planner as a new plan, "From a link"; a link missing one of them opens the quick-start with the rest filled in. Always include `birth`. Guide for people: [Build Your FIRE Plan With ChatGPT, Claude or Gemini](https://firenum.com/blog/fire-plan-with-ai-assistants).

## Calculators

13 free calculators, one question each. Inputs are kept in the browser and every result has a share link. Eleven work in 9 currencies; the Social Security and Roth ladder calculators are US dollars only. [All calculators](https://firenum.com/calculators).

### How much do I need?

- [FIRE Number Calculator](https://firenum.com/fire-number): 25 times a year's spending, from monthly spending alone, with your FIRE type (Lean, Traditional, Chubby, Fat).
- [Coast FIRE Calculator](https://firenum.com/coast-fire): can I stop saving and still retire on time? The amount invested today that grows to the FIRE number by retirement with no more savings; an optional Social Security or pension (amount, start age 62-70) lowers it.
- [Barista FIRE Calculator](https://firenum.com/barista-fire): how much less if I work part-time? The portfolio needed when part-time pay covers part of spending; optional ages for going part-time and stopping, and an optional Social Security or pension.
- [Lean FIRE Calculator](https://firenum.com/lean-fire): a frugal retirement, under $40,000 a year: the Lean FIRE number and a daily budget.
- [Fat FIRE Calculator](https://firenum.com/fat-fire): a comfortable retirement, $100,000+ a year: the Fat FIRE number and a daily budget.

### When can I retire?

- [FIRE Calculator](https://firenum.com/fire-calculator): your number and the age you reach it (see above).
- [When Can I Retire?](https://firenum.com/when-can-i-retire): the year your savings hit a target, a monthly income or a portfolio value.
- [Retirement Projector](https://firenum.com/retirement-projector): what your portfolio is worth at a retirement age, and the 4% monthly withdrawal it pays.
- [How Much to Save](https://firenum.com/how-much-to-save): the monthly savings that reach a target portfolio by a retirement age.

### Will my money last?

- [Retirement Withdrawal Calculator](https://firenum.com/retirement-withdrawal-calculator): the age your savings run out, from portfolio, monthly withdrawal, age, real return and an optional Social Security or pension; then how often the money lasts in 500 Monte Carlo runs and every US start year since 1872, on the Fire Planner's engine.
- [Monte Carlo Retirement Calculator](https://firenum.com/monte-carlo-retirement-calculator): does my money last in 500 random markets? The share of runs it lasts, the median and worst-10% money left, and the historical backtest since 1872.

### US taxes & Social Security

- [Social Security Break-Even](https://firenum.com/social-security-break-even): should I claim at 62, 67 or 70? The benefit at each age under SSA rules and the three break-even ages, from the statement's full-retirement-age benefit and birth year.
- [Roth Conversion Ladder](https://firenum.com/roth-conversion-ladder): how do I reach my 401(k) before 59½? The rung table with federal tax per year, the five-year bridge to fund, and the total tax against withdrawing early with the 10% penalty.

## A person to check your plan

- [Fee-Only Financial Advisors](https://firenum.com/financial-advisors): hand-picked fee-only advisors and coaches who work with early retirees. Flat or hourly fees, no commissions, and no one pays to be listed.
- [Retirement Plan Review](https://firenum.com/plan-review): a one-time review of your plan by a fee-only advisor at a partner registered investment adviser (RIA), for US residents. Not bookable yet: the page takes reservations and nothing is charged. firenum's referral fee is disclosed on the page.
- [How We Make Money](https://firenum.com/how-we-make-money): the planner and calculators are free; firenum earns only the referral fee the advisor pays on a plan review, disclosed on that page.

## Guides

- [What is FIRE?](https://firenum.com/guides/what-is-fire): FIRE from scratch: what it means, how the math works, whether it is realistic.
- [The 4% Rule: Does It Still Work?](https://firenum.com/guides/4-percent-rule): Bengen and the Trinity Study, what the rule says, its criticisms, and when to use 3.5% or 3%.
- [Where to Invest for FI](https://firenum.com/guides/where-to-invest): all-world ETFs (VT, VWCE) and brokerages in the US and EU.
- [How to Start Investing](https://firenum.com/guides/how-to-start-investing): from opening an account to automatic investing.
- [How to Use the Fire Planner](https://firenum.com/guides/how-to-use-the-fire-planner): step by step with screenshots, including US taxes.
- [Using the Fire Planner](https://firenum.com/guides/fire-progress-tracking): the whole planner, from the quick-start to check-ins, plans and the CSV.
- [How Projections Work](https://firenum.com/guides/progress-tracker-calculations) and [Mathematical Foundations](https://firenum.com/guides/progress-tracker-math): the formulas, default assumptions and derivations behind every Fire Planner number.
- [FIRE Types](https://firenum.com/fire-types): Lean, Coast, Barista, Chubby and Fat FIRE compared.
- [References & Methodology](https://firenum.com/references): Bengen, the Trinity Study, the 4% rule for 30+ year horizons, real vs nominal returns, default assumptions.
- [All guides](https://firenum.com/guides/).

## Research

- [Is the 4% Rule Dead? What Morningstar's 2026 Data Actually Says](https://firenum.com/blog/4-percent-rule-2026): Morningstar's 3.9%, flexible spending up to 6%, and what retirees actually withdraw.
- [How to Prepare Your FIRE Plan for High Inflation](https://firenum.com/blog/fire-high-inflation): sequence risk in 154 years of US data: almost every failed early retirement started in a high-inflation decade, and the spending rule that saved them.
- [Is a Financial Advisor Worth It?](https://firenum.com/blog/is-a-financial-advisor-worth-it): a 154-year backtest of selling after a crash; avoiding it cuts the risk of running out by more than 90%, if the fee is right.
- [How Much Do You Need to Retire at 35, 40, 45, and 50?](https://firenum.com/blog/how-much-to-retire-by-age): the number by age, the monthly savings, and how long the money must last.
- [Coast FIRE and Social Security: Claim at 62, 67 or 70?](https://firenum.com/blog/coast-fire-social-security): how a benefit lowers the Coast FIRE number, by age and claim age.
- [FIRE With 5% Bonds](https://firenum.com/blog/fire-high-bond-yields): what a TIPS ladder at 2.9% real changes for early retirees.
- [All research and reviews](https://firenum.com/blog/).

## Spreadsheets & data

Free Excel and Google Sheets downloads, no email, no sign-up: [all spreadsheets](https://firenum.com/tools).

- [FIRE Spreadsheet](https://firenum.com/tools/fire-spreadsheet): 9 tabs, from the FIRE number to the drawdown and a net worth log.
- [FIRE Backtest Spreadsheet](https://firenum.com/tools/fire-backtest-spreadsheet): any withdrawal rate against every US start year since 1872, formulas only; checks firenum's backtest independently.
- [FIRE Tracker Spreadsheet](https://firenum.com/tools/fire-tracker-spreadsheet): monthly net worth log with milestone dates.
- [Coast FIRE Spreadsheet](https://firenum.com/tools/coast-fire-spreadsheet): coast number, an age matrix and return scenarios.
- [FIRE Budget Template](https://firenum.com/tools/fire-budget-template): budget vs actual, savings rate and years to FI.
- [Savings Rate Spreadsheet](https://firenum.com/tools/savings-rate-spreadsheet): years to FI by savings rate and the savings a target age needs.
- [Shiller S&P 500 Monthly Returns](https://firenum.com/tools/shiller-data): the CSV/JSON of nominal monthly S&P 500 total returns since 1871 behind firenum's backtests; attribution to Robert J. Shiller required.

## How firenum compares

- ProjectionLab (Premium $129/year) and Boldin (PlannerPlus $168/year) are paid planners; the Fire Planner covers Monte Carlo, a historical backtest since 1872 and US taxes (federal, state, payroll, Social Security, Roth conversions, RMDs) for free, with no account.
- Where they go further: tax outside the US, capital gains harvesting and estate planning (ProjectionLab); account linking and a CFP you can hire (Boldin); optimizers that pick a claiming age or Roth conversions for you (MaxiFi, Pralana).
- Prices and features checked on each vendor's page: [Retirement Planner Comparison, October 2026](https://firenum.com/blog/retirement-planner-comparison-october-2026).

## About

- [About](https://firenum.com/about): the founder's story and why retiring early is not just for the wealthy.
- [Account](https://firenum.com/account): the optional free account (email link, password or Google): the plans it keeps, the emails switch, delete account.
- [Contact](https://firenum.com/contact): questions, feedback and bug reports, contact@firenum.com.
- [Press](https://firenum.com/press) and [Careers](https://firenum.com/careers).
- Built with Astro and Preact on Cloudflare Workers. The planner and calculators run in the browser; the agent endpoints (MCP, REST, A2A) run the same engine on a Cloudflare Worker and store nothing.

## Agent API

Three ways for AI agents to answer FIRE questions with the Fire Planner: an MCP server, a REST API and an A2A endpoint. All take the same structured financial data and return the planner's answer for it, plus a URL that opens it in the Fire Planner. A link with an age (`birth`), spending and income opens as a new plan, "From a link", beside the reader's own; a link missing one of them opens the quick-start with the data filled in, to finish it. Always send `birth`. The calling LLM handles inference ("I make $80k" → `salary: 80000`), the API the deterministic part: the plan the link makes, graded as the planner grades it.

The `answer` is the planner's own words, as the plan shows once opened (average returns, today's money, their currency): `headline` (when they can retire and how long the money lasts, or why no date works), `monte_carlo` and `backtest` (how often that survives 500 simulated markets and every historical start year since 1872; a low count means the date is on a knife edge), `money_left`, `spending_room` (with a retirement year of their own), `coast` (could they stop saving today), `fire_number` (25 × a year's spending), `coast_number` and `coast_age` (what they would need invested today to stop saving and still reach the FIRE number by their retirement age, or 65, at the plan's growth less inflation), `assumed` (what it assumed that they did not say: without `salary` or `side_income`, an income that covers spending, contributions and debt payments until retirement), `missing` (what the planner needs before it can answer), `assumptions` (what the answer rests on: the rates, how each model works, each of their lines as the planner read it, and what is not modeled) and `table` (net worth year by year in today's money on each model). A field that does not apply is left out. To grade another retirement year, call again with `retire`.

### MCP server: `https://firenum.com/mcp`

For ChatGPT, Claude and any MCP client. Streamable HTTP, no auth, one tool: `build_retirement_plan`, the REST operation below (same parameters, same `{ url, params_applied, answer }` result as `structuredContent`). Claude: the connector directory (https://claude.ai/directory/connectors/firenum) or Customize → Connectors → Add custom connector. Claude Code: `claude mcp add --transport http firenum https://firenum.com/mcp`. ChatGPT: chatgpt.com/plugins (+ → Add custom MCP server). Le Chat: Connectors → + Add Connector → Custom MCP Connector. Perplexity (Pro and up): Account settings → Connectors → + Custom connector → Remote (authentication None). Gemini (personal US accounts, 18+, English): Settings → Connected Apps → Add a custom app. MCP Registry name: `com.firenum/fire-planner`.

### REST API: `POST /api/fire-plan`

For ChatGPT Actions, LangChain, CrewAI, or any OpenAPI consumer.

```
POST https://firenum.com/api/fire-plan
Content-Type: application/json

{"birth": 1990, "retire_age": 55, "salary": 80000, "retirement": 200000, "expenses": 4000}

→ {"url": "https://firenum.com/fire-planner?birth=1990&retire_age=55&salary=80000&retirement=200000&expenses=4000&source=agent", "params_applied": ["birth", "retire_age", "salary", "retirement", "expenses"], "answer": {"headline": "Retiring Jan 2045, at 55: money lasts to age 90", "monte_carlo": "money lasts in 230 of 500 simulations", "backtest": "money lasts in 100 of 100 start years", "money_left": "Money left at age 90: $1.56M", "spending_room": "You could spend up to $4,650/mo and the money still lasts to age 90", "coast": "If you stopped saving today and still retired Jan 2045, the money runs out in 2055.", "fire_number": 1200000, "coast_number": 569571, "coast_age": 55}}
```

The answer is the planner's for the month you call (Oct 2026 above): dates and counts move with it. `assumptions` and `table` are left out of the example for length.

### A2A JSON-RPC: `POST /a2a`

Google A2A protocol. Send `message/send` with a DataPart containing financial params.

```
POST https://firenum.com/a2a
Content-Type: application/json

{"jsonrpc": "2.0", "id": "1", "method": "message/send", "params": {"message": {"role": "user", "parts": [{"kind": "data", "data": {"birth": 1990, "salary": 80000, "expenses": 4000}}]}}}

→ JSON-RPC response: a completed task whose artifact holds { url, params_applied, answer } and the headline with both counts as text
```

Agent card: https://firenum.com/.well-known/agent-card.json

### Direct URL Construction

Agents can also construct URLs directly — no API call needed:
`https://firenum.com/fire-planner?salary=80000&expenses=4000&source=agent`

**All params optional. Income = annual. Expenses & contributions = monthly. Amounts in whole currency units. Always include `source=agent` and `birth`: with `birth`, spending and income the link opens the plan directly; without one of them it opens the quick-start.**

| Param | What | Example |
|-------|------|---------|
| `birth` | Birth year (from an age: current year minus age) | `1990` |
| `retire` | Retirement year | `2045` |
| `retire_age` | Retirement age (needs `birth`) | `55` |
| `currency` | USD, EUR, GBP, JPY, CAD, AUD, CHF, INR, NZD (default USD) | `EUR` |
| `salary` | Annual gross salary as given (grows 3%/yr; untaxed unless `taxes=us`: otherwise a tax amount they gave goes in expenses) | `80000` |
| `side_income` | Annual side income | `12000` |
| `part_time_income` | Annual part-time income in retirement (Barista FIRE) | `18000` |
| `part_time_until` | Age the part-time income stops (needs `birth`; 100 or omitted = for life) | `60` |
| `pension` | Annual pension | `24000` |
| `social_security` | Annual Social Security | `20000` |
| `rental_income` | Annual rental income | `18000` |
| `retirement` | Retirement account balance (market rate, default 7%) | `200000` |
| `retirement_contribution` | Monthly contribution | `1500` |
| `roth` | Roth account balance (market rate, default 7%) | `50000` |
| `roth_contribution` | Monthly contribution | `500` |
| `brokerage` | Taxable brokerage balance (market rate, default 7%) | `100000` |
| `brokerage_contribution` | Monthly contribution | `500` |
| `savings` | High-yield savings balance (4.5% growth) | `20000` |
| `savings_contribution` | Monthly contribution | `200` |
| `hsa` | HSA balance (market rate, default 7%) | `15000` |
| `hsa_contribution` | Monthly contribution | `300` |
| `cash` | Cash/checking balance (0% growth) | `5000` |
| `cash_contribution` | Monthly contribution | `100` |
| `real_estate` | Real estate equity (4% growth) | `300000` |
| `real_estate_contribution` | Monthly contribution (e.g. extra principal) | `500` |
| `crypto` | Crypto balance (0% growth) | `10000` |
| `crypto_contribution` | Monthly contribution | `100` |
| `expenses` | Total monthly spending. Send it OR categories; if both, categories count inside this total (never on top) | `4000` |
| `housing` | Monthly housing | `1800` |
| `healthcare` | Monthly healthcare | `300` |
| `food` | Monthly food | `600` |
| `transportation` | Monthly transportation | `400` |
| `utilities` | Monthly utilities | `200` |
| `insurance` | Monthly insurance | `300` |
| `discretionary` | Monthly discretionary | `500` |
| `debt` | Debt balance | `25000` |
| `debt_rate` | Debt interest rate (%) | `5.5` |
| `debt_payment` | Monthly debt payment | `400` |
| `debt_name` | Debt label | `Student Loan` |
| `target` | Accepted from older links and ignored: the planner answers with a retirement date, not a target | `1200000` |
| `growth` | Market rate for retirement, Roth, brokerage and HSA; also overrides the other assets' fixed defaults (%, default 7) | `7` |
| `inflation` | Inflation rate for all expenses (%, default 3) | `3` |
| `taxes` | `us` computes US federal, state and payroll tax (income before tax, amounts in dollars); `off` (default) takes income as take-home pay | `us` |
| `state` | US state code for state income tax (without it, federal only) | `CA` |
| `partner_birth` | Partner's birth year (retires at the same time; every line stays the first person's) | `1988` |
| `married` | With a partner, files jointly (default `true`); `false` files as two singles | `true` |
| `dependents` | Dependents' birth years, comma-separated | `2015,2018` |
| `pia` | Monthly Social Security at full retirement age, from the SSA statement | `2400` |
| `claim_age` | Social Security claiming age, 62-70 (default 67) | `67` |
| `roth_conversion` | Roth ladder: `none`, `fill_10`, `fill_12`, `fill_22`, `fill_24`, `fixed`, `aca`; needs a `roth` account to convert into | `fill_12` |
| `roth_conversion_amount` | Dollars a year with `roth_conversion=fixed` | `30000` |
| `roth_conversion_until` | Age the conversions stop (default 72) | `72` |
| `source` | Set to `agent`: the link becomes a new plan, "From a link" (without it the planner shows a shared plan that saves nothing) | `agent` |

OpenAPI spec (the authoritative contract; this table mirrors it): https://firenum.com/openapi.yaml

## Legal

- [Privacy Policy](https://firenum.com/privacy): on the website, numbers stay in the browser; numbers an AI assistant sends to the API are used for the answer and never stored. With a free account, the email and the plans saved under it are stored (Cloudflare KV) until Delete account. Cookieless Cloudflare Web Analytics; Google Analytics, Microsoft Clarity and the Reddit Pixel only after cookie consent.
- [Terms of Service](https://firenum.com/terms): educational tool, not financial advice.