{
  "id": "percentage",
  "version": "aac729e624c1",
  "status": "published",
  "name": "Percentage Calculator",
  "question": "How do I work out a percentage?",
  "summary": "Computes a percentage of a number, what percent one number is of another, or the whole number from a part and a percent.",
  "category": "math",
  "subcategory": "arithmetic",
  "url": "https://www.acalculator.org/math/percentage-calculator",
  "markdown": "https://www.acalculator.org/math/percentage-calculator.md",
  "kind": "formulas",
  "method": "R = P ÷ 100 × V: the part R is P percent of the whole number V.",
  "assumptions": [
    "Percentages are in percent points: 18 means 18%.",
    "Solving for the percent or the whole number divides by the other one, so there is no answer when it is 0."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "percentage": {
        "title": "Percent",
        "description": "The percentage, in percent points (18 means 18%).",
        "type": "number",
        "x-unit": "percent"
      },
      "value": {
        "title": "Of",
        "description": "The whole number the percentage is taken of.",
        "type": "number"
      },
      "result": {
        "title": "Is",
        "description": "The part: the percentage of the whole number.",
        "type": "number"
      }
    }
  },
  "solve": {
    "fillAny": 2,
    "variables": [
      "percentage",
      "value",
      "result"
    ],
    "inputsOnly": []
  },
  "outputs": {
    "percent": {
      "label": "Percent",
      "description": "The percentage, in percent points (18 means 18%).",
      "format": "percent"
    },
    "value": {
      "label": "Of",
      "description": "The whole number the percentage is taken of.",
      "format": "number"
    },
    "result": {
      "label": "Is",
      "description": "The part: the percentage of the whole number.",
      "format": "number"
    },
    "plus": {
      "label": "The number plus the percent",
      "description": "The whole number increased by the percentage: V + R.",
      "format": "number"
    },
    "minus": {
      "label": "The number minus the percent",
      "description": "The whole number decreased by the percentage: V − R.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "percentage": 18,
      "value": 240
    },
    "outputs": {
      "result": 43.199999999999996,
      "plus": 283.2,
      "minus": 196.8
    },
    "text": "18% of 240 is 43.2."
  },
  "examples": [
    {
      "given": {
        "percentage": 18,
        "value": 240
      },
      "expect": {
        "result": 43.2,
        "plus": 283.2,
        "minus": 196.8
      },
      "source": "hand calculation in content.mdx: 18 ÷ 100 × 240 = 43.2; 240 + 43.2 = 283.2; 240 − 43.2 = 196.8; OpenStax, Prealgebra 2e, §6.2 Solve General Applications of Percent. https://openstax.org/books/prealgebra-2e/pages/6-2-solve-general-applications-of-percent"
    },
    {
      "given": {
        "result": 43.2,
        "value": 240
      },
      "expect": {
        "percentage": 18
      },
      "source": "hand calculation in content.mdx: 43.2 ÷ 240 × 100 = 18%; OpenStax, Prealgebra 2e, §6.2 Solve General Applications of Percent. https://openstax.org/books/prealgebra-2e/pages/6-2-solve-general-applications-of-percent"
    },
    {
      "given": {
        "percentage": 25,
        "result": 15
      },
      "expect": {
        "value": 60
      },
      "source": "hand calculation in content.mdx: 15 ÷ 25 × 100 = 60 (old page FAQ: 15 is 25% of 60); OpenStax, Prealgebra 2e, §6.2 Solve General Applications of Percent. https://openstax.org/books/prealgebra-2e/pages/6-2-solve-general-applications-of-percent"
    }
  ],
  "sources": [
    "OpenStax, Prealgebra 2e, §6.2 Solve General Applications of Percent. https://openstax.org/books/prealgebra-2e/pages/6-2-solve-general-applications-of-percent"
  ],
  "related": [],
  "changelog": [
    {
      "date": "2026-09-29",
      "note": "Worked examples name a published reference for their rule."
    }
  ]
}