{
  "id": "rule-of-72-calculator",
  "version": "1.0.0",
  "name": "Rule of 72 Calculator",
  "shortName": "Rule of 72",
  "description": "Estimate doubling time and compare it with the exact compound-growth result.",
  "category": "Finance",
  "categorySlug": "finance",
  "keywords": [
    "doubling time",
    "rule 72",
    "investment rate",
    "compound growth"
  ],
  "status": "live",
  "workStatus": "pending",
  "reviewStatus": "pending",
  "migrationStatus": "new",
  "engine": "native",
  "creator": null,
  "reviewer": null,
  "quality": {
    "availability": "live",
    "technicalReviewRecord": "/reviews/rule-of-72-calculator.json",
    "qualifiedReview": "pending",
    "qualifiedReviewer": null,
    "qualifiedReviewDate": null,
    "formulaVersion": "1.0.0",
    "referenceCoverage": "references-pending",
    "releaseTestScope": "Catalog and regression checks are not a professional formula audit; consult release evidence.",
    "historicalMetadataDate": "2026-08-18",
    "historicalMetadataNotice": "The imported date is not evidence of a completed human review."
  },
  "urls": {
    "page": "/calculator/rule-of-72-calculator/",
    "definition": "/calculator/rule-of-72-calculator/definition.json",
    "schema": "/calculator/rule-of-72-calculator/schema.json",
    "llms": "/calculator/rule-of-72-calculator/llms.txt",
    "legacyDefinition": "/calculator/rule-of-72-calculator.json"
  },
  "queryExample": "https://askcalculators.com/calculator/rule-of-72-calculator/?annualRate=8",
  "queryParameters": {
    "annualRate": {
      "label": "Annual growth rate",
      "type": "percent",
      "required": true,
      "default": 8
    }
  },
  "inputs": [
    {
      "id": "annualRate",
      "label": "Annual growth rate",
      "type": "percent",
      "required": true,
      "defaultValue": 8,
      "min": 0.01,
      "max": 100,
      "step": 0.1,
      "control": "slider-number",
      "width": "full"
    }
  ],
  "outputs": [
    {
      "id": "ruleOf72Years",
      "label": "Rule of 72 doubling time",
      "format": "number",
      "digits": 2,
      "suffix": " years",
      "primary": true
    },
    {
      "id": "exactYears",
      "label": "Exact doubling time",
      "format": "number",
      "digits": 2,
      "suffix": " years"
    },
    {
      "id": "difference",
      "label": "Approximation difference",
      "format": "number",
      "digits": 2,
      "suffix": " years"
    }
  ],
  "formula": {
    "expression": "Estimated doubling years = 72 ÷ annual rate",
    "note": "The exact result is ln(2) ÷ ln(1 + rate)."
  },
  "examples": [
    {
      "label": "Reproducible default-input example (not a personal recommendation)",
      "inputs": {
        "annualRate": 8
      }
    }
  ],
  "sources": []
}