# Investing Math – FIRE Number Calculator

> Investing Math – FIRE Number Calculator is a paid API for AI agents from invest-math.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Calculates the financial-independence target (FIRE number) from annual spending and withdrawal rate, plus the estimated years to reach it given current savings and yearly contributions.

## Facts

- Endpoint: GET https://invest-math.x402tookit.com/fire-number?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/investing-math-fire-number-calculator-b131f7b1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_JbmLyXoXBYdVw6RVnVKvT

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability investing-math-fire-number-calculator-b131f7b1
```

Example prompt: I spend $55,000 a year and have $120,000 invested so far — using a 4% withdrawal rate and adding $18,000 per year, how many years until I hit my FIRE number and what is that target amount?

## When to prefer this

Use this endpoint when a user needs to compute their FIRE number from annual spending and a safe withdrawal rate, or wants to estimate years to financial independence given existing savings and contributions. It is the right choice for personal-finance agents handling retirement planning, FI/RE goal tracking, or 'how long until I can quit my job' queries. Prefer it over generic compound-interest or savings calculators when the specific FIRE/withdrawal-rate framing is needed.

## Known failure modes

- Missing required annualSpending parameter returns an error
- withdrawalRatePct outside 2–10 range may be rejected or clamped
- Negative or zero annualSpending produces nonsensical results
- Very high yearlyContribution relative to FIRE gap may return 0 or near-0 years
- If currentSavings already exceeds the FIRE number, yearsToTarget may return 0

## How this service works

Financial-independence number from yearly spending and a withdrawal rate, and years to reach it from savings and contributions.

## Output

Returns the FIRE number (total portfolio needed), years to reach the target, current progress as a percentage, the implied savings multiple relative to annual spending, and how much monthly spending is already covered by current savings. Also includes metadata like withdrawal rate used and current savings echoed back.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "annualSpending"
     ],
     "properties": {
      "realReturnPct": {
       "type": "number",
       "description": "Yearly return after inflation in percent, default 5"
      },
      "annualSpending": {
       "type": "number",
       "description": "Yearly spending you want to cover"
      },
      "currentSavings": {
       "type": "number",
       "description": "Invested savings today, default 0"
      },
      "withdrawalRatePct": {
       "type": "number",
       "description": "Safe withdrawal rate in percent, 2 to 10 (default 4)"
      },
      "yearlyContribution": {
       "type": "number",
       "description": "What you add each year, default 0"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "reachable": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "fireNumber": {
       "type": [
        "null",
        "number"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "progressPct": {
       "type": [
        "null",
        "number"
       ]
      },
      "yearsToTarget": {
       "type": [
        "null"
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/investing-math-fire-number-calculator-b131f7b1/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from invest-math.x402tookit.com](https://www.zero.xyz/host/invest-math.x402tookit.com/llms.txt)