# Automotive Gear RPM Calculator

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

Calculates engine RPM at a given road speed (or speed at a given RPM) based on tire size, axle ratio, and transmission gear ratios, returning a per-gear table.

## Facts

- Endpoint: GET https://automotive-calc.x402tookit.com/gear-rpm?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/automotive-gear-rpm-calculator-e0d1c608
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_3u4G5gGxh4wkFYPnxaz88

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 automotive-gear-rpm-calculator-e0d1c608
```

Example prompt: What RPM will my engine be at 70 mph in each gear? My truck has 265/70R17 tires, a 3.73 axle ratio, and gear ratios of 1:3.59, 2:2.19, 3:1.41, 4:1.00, 5:0.83.

## When to prefer this

Use this endpoint when you need precise drivetrain RPM-to-speed or speed-to-RPM calculations based on actual tire size, axle ratio, and multi-gear transmission ratios. Ideal for automotive enthusiasts, mechanics, or fleet managers evaluating gear swaps, tire upsizing, or engine operating ranges across all gears simultaneously.

## Known failure modes

- Missing required tire or axleRatio parameters returns a validation error
- Malformed tire size string (e.g. not in NNN/NNRNN format or plain inches) may cause a parse error
- Neither speed nor rpm provided causes ambiguous or error response
- Axle ratio outside 1–8 range may produce invalid results
- Gear ratio string not formatted as 'gear:ratio; gear:ratio' may fail to parse

## How this service works

Engine RPM at a road speed (or speed at an RPM) from tire size, axle ratio and transmission gear ratios, with a table by gear.

## Output

Returns a JSON object containing the calculated road speed or engine RPM, a per-gear table showing each gear name, gear ratio, overall ratio, and RPM at the given speed (or speed at the given RPM), plus the tire diameter in inches, axle ratio used, speed unit, a summary string, and any disclaimer or degraded-data flags.

## 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": [
      "tire",
      "axleRatio"
     ],
     "properties": {
      "rpm": {
       "type": "number",
       "description": "Engine RPM, to find the speed instead"
      },
      "tire": {
       "type": "string",
       "description": "Tire size like 265/70R17, or a diameter in inches like 28"
      },
      "gears": {
       "type": "string",
       "description": "Gear ratios as gear:ratio separated by semicolons, for example '1:3.59; 2:2.19; 3:1.41; 4:1.00; 5:0.83'"
      },
      "speed": {
       "type": "number",
       "description": "Road speed (give this, or rpm)"
      },
      "axleRatio": {
       "type": "number",
       "description": "Final drive (axle) ratio, 1 to 8, for example 3.73"
      },
      "gearRatio": {
       "type": "number",
       "description": "One transmission gear ratio (default 1, direct drive); use gears for several"
      },
      "speedUnit": {
       "type": "string",
       "description": "mph (default) or kmh"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "gears": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "object",
        "properties": {
         "rpm": {
          "type": [
           "null",
           "number"
          ]
         },
         "gear": {
          "type": [
           "null",
           "string"
          ]
         },
         "gearRatio": {
          "type": [
           "null",
           "number"
          ]
         },
         "overallRatio": {
          "type": [
           "null",
           "number"
          ]
         }
        }
       }
      },
      "speed": {
       "type": [
        "null",
        "number"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
    
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/automotive-gear-rpm-calculator-e0d1c608/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from automotive-calc.x402tookit.com](https://www.zero.xyz/host/automotive-calc.x402tookit.com/llms.txt)