{
  "id": "engine-horsepower-calculator",
  "version": "20.13.0",
  "name": "Estimate Engine Output from Torque and RPM",
  "shortName": "Engine power",
  "description": "Calculate engine power from measured torque and speed, with displacement-specific output and an explicit legacy airflow fallback.",
  "category": "Vehicles & Travel",
  "categorySlug": "vehicles-travel",
  "keywords": [
    "engine power",
    "torque",
    "rpm"
  ],
  "status": "live",
  "workStatus": "pending",
  "reviewStatus": "pending",
  "migrationStatus": "new",
  "engine": "native",
  "creator": null,
  "reviewer": null,
  "quality": {
    "availability": "live",
    "technicalReviewRecord": "/reviews/engine-horsepower-calculator.json",
    "qualifiedReview": "pending",
    "qualifiedReviewer": null,
    "qualifiedReviewDate": null,
    "formulaVersion": "20.13.0",
    "referenceCoverage": "references-pending",
    "releaseTestScope": "Catalog and regression checks are not a professional formula audit; consult release evidence.",
    "historicalMetadataDate": "2026-09-10",
    "historicalMetadataNotice": "The imported date is not evidence of a completed human review."
  },
  "urls": {
    "page": "/us/engine-horsepower/",
    "definition": "/us/engine-horsepower/definition.json",
    "schema": "/us/engine-horsepower/schema.json",
    "llms": "/us/engine-horsepower/llms.txt",
    "legacyDefinition": "/us/engine-horsepower/definition.json"
  },
  "queryExample": "https://askcalculators.com/us/engine-horsepower/?displacement=2&cylinders=4&rpm=4000&efficiency=0.85&torqueNm=300",
  "queryParameters": {
    "displacement": {
      "label": "Displacement (L)",
      "type": "number",
      "required": true,
      "default": 5
    },
    "cylinders": {
      "label": "Cylinders",
      "type": "number",
      "required": true,
      "default": 8
    },
    "rpm": {
      "label": "Engine speed (RPM)",
      "type": "number",
      "required": true,
      "default": 6000
    },
    "efficiency": {
      "label": "Legacy airflow efficiency (used only without torque)",
      "type": "number",
      "required": true,
      "default": 0.85
    },
    "torqueNm": {
      "label": "Measured torque at entered RPM (N·m, optional)",
      "type": "number",
      "required": false
    }
  },
  "inputs": [
    {
      "id": "displacement",
      "label": "Displacement (L)",
      "type": "number",
      "defaultValue": 5,
      "required": true,
      "min": 0.01
    },
    {
      "id": "cylinders",
      "label": "Cylinders",
      "type": "number",
      "defaultValue": 8,
      "required": true,
      "min": 1
    },
    {
      "id": "rpm",
      "label": "Engine speed (RPM)",
      "type": "number",
      "defaultValue": 6000,
      "required": true,
      "min": 0
    },
    {
      "id": "efficiency",
      "label": "Legacy airflow efficiency (used only without torque)",
      "type": "number",
      "defaultValue": 0.85,
      "required": true,
      "min": 0.01
    },
    {
      "id": "torqueNm",
      "label": "Measured torque at entered RPM (N·m, optional)",
      "type": "number",
      "min": 0,
      "help": "When provided, torque and RPM replace the legacy airflow heuristic."
    }
  ],
  "outputs": [
    {
      "id": "horsepower",
      "label": "Mechanical horsepower",
      "format": "number",
      "primary": true,
      "digits": 2
    },
    {
      "id": "kilowatts",
      "label": "Power (kW)",
      "format": "number",
      "primary": false,
      "digits": 2
    },
    {
      "id": "horsepowerPerLitre",
      "label": "Horsepower per litre",
      "format": "number",
      "primary": false,
      "digits": 2
    },
    {
      "id": "litresPerCylinder",
      "label": "Litres per cylinder",
      "format": "number",
      "primary": false,
      "digits": 2
    }
  ],
  "formula": {
    "expression": "Power (W) = torque (N·m) × RPM × 2π / 60; mechanical hp = W / 745.699871582.",
    "note": "Without torque: legacy airflow hp = litres × 61.0237 × RPM × efficiency / 3456 / 1.4."
  },
  "examples": [
    {
      "label": "Torque-based operating point",
      "inputs": {
        "displacement": 2,
        "cylinders": 4,
        "rpm": 4000,
        "efficiency": 0.85,
        "torqueNm": 300
      }
    }
  ],
  "sources": [],
  "publicSlug": "engine-horsepower",
  "namespace": "us",
  "countries": [
    "us"
  ]
}