# Bicycle Gear Ratio & Speed Calculator

> Bicycle Gear Ratio & Speed Calculator is a paid API for AI agents from bike-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Calculates gear ratio, gear inches, development per pedal turn, and speed at a given cadence for a specific chainring and cog combination on a bicycle wheel.

## Facts

- Endpoint: GET https://bike-calc.x402tookit.com/gear-ratio?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/bicycle-gear-ratio-speed-calculator-5066c7ba
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8AFRQQBMGK90aOpRr4WGx

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 bicycle-gear-ratio-speed-calculator-5066c7ba
```

Example prompt: What gear ratio, gear inches, and speed will I get at 90 rpm with a 50-tooth chainring and a 17-tooth cog on 700x25c tyres?

## When to prefer this

Use this endpoint when you need precise single-gear-combination calculations including gear ratio, gear inches, development, and speed at cadence. It is ideal for evaluating a specific chainring/cog pairing before a ride or when building a gear recommendation tool. Prefer the full drivetrain matrix endpoint (sibling) if you need all combinations across a cassette at once.

## Known failure modes

- Missing required chainring or cog parameters returns an error
- Non-integer chainring or cog values cause validation failure
- Unrecognised tyre preset string falls back to default 700x25c or may error
- Cadence of 0 or negative values may produce nonsensical speed outputs
- Providing both diameterInches and circumferenceMm may cause ambiguity — only one override should be used

## How this service works

Gear ratio, gear inches, development per pedal turn and speed at a cadence for a chainring and cog on a given wheel.

## Output

Returns the gear ratio (chainring/cog), gear inches (effective wheel diameter driven per crank revolution), development in meters (distance per pedal stroke), speed in both km/h and mph at the specified cadence, meters per minute, and the wheel circumference and diameter used in the calculation.

## 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": [
      "chainring",
      "cog"
     ],
     "properties": {
      "cog": {
       "type": "integer",
       "description": "Rear cog teeth (for example 17)"
      },
      "wheel": {
       "type": "string",
       "description": "Tyre preset: 700x23c, 700x25c, 700x28c, 700x32c, 700x35c, 700x38c, 26x2.0 (default 700x25c)"
      },
      "cadence": {
       "type": "number",
       "description": "Pedalling cadence in rpm (default 90)"
      },
      "chainring": {
       "type": "integer",
       "description": "Chainring teeth (for example 50)"
      },
      "diameterInches": {
       "type": "number",
       "description": "Wheel diameter in inches instead (for example 26 for a 26 inch wheel)"
      },
      "circumferenceMm": {
       "type": "number",
       "description": "Rolling circumference in mm instead of a preset (measure it on the bike)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "cog": {
       "type": [
        "null",
        "number"
       ]
      },
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "ratio": {
       "type": [
        "null",
        "number"
       ]
      },
      "source": {
       "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"
       ]
      },
      "chainring": {
      
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/bicycle-gear-ratio-speed-calculator-5066c7ba/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from bike-calc.x402tookit.com](https://www.zero.xyz/host/bike-calc.x402tookit.com/llms.txt)