# Running Pace & Race Prediction Calculator

> Running Pace & Race Prediction Calculator is a paid API for AI agents from fitness-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).

Calculates running pace per km and per mile, speed in km/h and mph, and predicts finish times for other race distances using the Riegel formula from a given distance and finish time.

## Facts

- Endpoint: GET https://fitness-calc.x402tookit.com/pace-race?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/running-pace-race-prediction-calculator-7e01651b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_xbL6O8wsJsbpXDVbe50uy

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 running-pace-race-prediction-calculator-7e01651b
```

Example prompt: I ran a half marathon in 1:52:30 — what's my pace per km and per mile, and what would the Riegel formula predict for my marathon finish time?

## When to prefer this

Choose this endpoint when you need to compute running pace, speed, or cross-distance race time predictions from a single known race result. It is purpose-built for endurance running metrics and applies the established Riegel formula for predictions, making it ideal for runners analyzing performance or setting race goals. Prefer it over generic calculators when you need both pace units (per km and per mile) and structured predictions for multiple race distances in a single call.

## Known failure modes

- Missing required 'distance' or 'time' query parameters returns an error
- Unrecognized distance format (not a number with unit or named distance like '5k', 'marathon') returns a parse error
- Malformed time string (not m:ss or h:mm:ss format) returns a validation error
- Extremely short distances or times may yield unreliable Riegel predictions

## How this service works

Running pace per km and per mile, speed, and predicted times for other race distances using the Riegel formula.

## Output

Returns pace per km (e.g. '5:12/km'), pace per mile (e.g. '8:22/mi'), speed in km/h and mph, distance in both km and miles, time in seconds, and a predictions object with Riegel-formula estimated finish times for standard race distances including mile, 1500m, 3k, 5k, 10k, half marathon, and marathon.

## 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": [
      "distance",
      "time"
     ],
     "properties": {
      "time": {
       "type": "string",
       "description": "Finish time as m:ss or h:mm:ss"
      },
      "distance": {
       "type": "string",
       "description": "Distance: a number with unit (5km, 3.1mi, 800m) or a name: 5k, 10k, half, marathon, mile"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "time": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "formula": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "speedKmh": {
       "type": [
        "null",
        "number"
       ]
      },
      "speedMph": {
       "type": [
        "null",
        "number"
       ]
      },
      "pacePerKm": {
       "type": [
        "null",
        "string"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "distanceKm": {
       "type": [
        "null",
        "number"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "pacePerMile": {
       "type": [
        "null",
        "string"
       ]
      },
      "predictions": {
       "type": [
        "null",
       
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/running-pace-race-prediction-calculator-7e01651b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from fitness-calc.x402tookit.com](https://www.zero.xyz/host/fitness-calc.x402tookit.com/llms.txt)