{
  "id": "rf-value",
  "version": "49c6b8530f82",
  "status": "published",
  "name": "Rf Value Calculator",
  "question": "What is the Rf value?",
  "summary": "Finds the retention factor (Rf) of a spot in thin-layer or paper chromatography: the distance the spot moved divided by the distance the solvent front moved, or either distance from the other and the Rf.",
  "category": "chemistry",
  "subcategory": "solutions",
  "url": "https://www.acalculator.org/chemistry/rf-value-calculator",
  "markdown": "https://www.acalculator.org/chemistry/rf-value-calculator.md",
  "kind": "function",
  "method": "Rf = distance the spot moved ÷ distance the solvent front moved, both measured from the baseline; spot distance = Rf × front distance; front distance = spot distance ÷ Rf.",
  "assumptions": [
    "Both distances are measured from the baseline (origin) on the same plate: to the middle of the spot and to the solvent front.",
    "The spot cannot move past the front, so the Rf is from 0 to 1. The Rf is shown to 2 decimals, rounded half up from its exact value."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "find": {
        "title": "Find",
        "description": "Which value to work out: the Rf, the spot’s distance, or the solvent front’s distance.",
        "type": "string",
        "enum": [
          "rf",
          "spot",
          "front"
        ]
      },
      "d": {
        "title": "Distance the spot moved",
        "description": "From the baseline (where the sample was put) to the middle of the spot.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "minimum": 0,
        "maximum": 1
      },
      "f": {
        "title": "Distance the solvent front moved",
        "description": "From the baseline to the solvent front, marked when the plate was taken out.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "exclusiveMinimum": 0,
        "maximum": 1
      },
      "rf": {
        "title": "Rf value",
        "description": "The retention factor, from 0 (the spot stayed on the baseline) to 1 (it moved with the front).",
        "type": "number",
        "minimum": 0,
        "maximum": 1
      }
    }
  },
  "outputs": {
    "result": {
      "label": "Answer",
      "description": "The Rf to 2 decimals, or the distance worked out in mm and cm.",
      "format": "text"
    },
    "rfValue": {
      "label": "Rf (full)",
      "description": "The retention factor to 6 significant figures.",
      "format": "number"
    },
    "percent": {
      "label": "Share of the front’s distance (%)",
      "description": "How far the spot moved, as a percent of the front’s distance.",
      "format": "number"
    },
    "spotMm": {
      "label": "Spot distance (mm)",
      "description": "The distance from the baseline to the middle of the spot, in millimeters.",
      "format": "number"
    },
    "frontMm": {
      "label": "Front distance (mm)",
      "description": "The distance from the baseline to the solvent front, in millimeters.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "find": "rf",
      "d": "22 mm",
      "f": "40 mm",
      "rf": 0.55
    },
    "outputs": {
      "result": "Rf = 0.55",
      "rfValue": 0.55,
      "percent": 55,
      "spotMm": 22,
      "frontMm": 40
    },
    "text": "Rf = 0.55: the spot moved 55% as far as the solvent front."
  },
  "examples": [
    {
      "given": {
        "find": "rf",
        "d": 0.022,
        "f": 0.04
      },
      "expect": {
        "result": "Rf = 0.55",
        "rfValue": 0.55,
        "percent": 55
      },
      "source": "LibreTexts, Nichols, Organic Chemistry Lab Techniques, §2.3C The Retention Factor (Rf = distance traveled by the compound ÷ distance traveled by the solvent front), https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_Lab_Techniques_(Nichols)/02%3A_Chromatography/2.03%3A_Thin_Layer_Chromatography_(TLC)/2.3C%3A_The_Retention_Factor, Figure 2.14a: 22 mm ÷ 40 mm = 0.55"
    },
    {
      "given": {
        "find": "rf",
        "d": 0.0069,
        "f": 0.02
      },
      "expect": {
        "result": "Rf = 0.35",
        "rfValue": 0.345
      },
      "source": "hand calculation in content.mdx: 6.9 ÷ 20 = 0.345 exactly, half up to 2 decimals 0.35"
    },
    {
      "given": {
        "find": "spot",
        "rf": 0.35,
        "f": 0.05
      },
      "expect": {
        "spotMm": 17.5,
        "result": "Spot distance = 17.5 mm (1.75 cm)"
      },
      "source": "LibreTexts, Nichols, Organic Chemistry Lab Techniques, §2.3C The Retention Factor (Rf = distance traveled by the compound ÷ distance traveled by the solvent front), https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_Lab_Techniques_(Nichols)/02%3A_Chromatography/2.03%3A_Thin_Layer_Chromatography_(TLC)/2.3C%3A_The_Retention_Factor (Rf formula); hand calculation in content.mdx: 0.35 × 50 mm = 17.5 mm"
    },
    {
      "given": {
        "find": "front",
        "rf": 0.55,
        "d": 0.033
      },
      "expect": {
        "frontMm": 60,
        "result": "Solvent front distance = 60 mm (6 cm)"
      },
      "source": "LibreTexts, Nichols, Organic Chemistry Lab Techniques, §2.3C The Retention Factor (Rf = distance traveled by the compound ÷ distance traveled by the solvent front), https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_Lab_Techniques_(Nichols)/02%3A_Chromatography/2.03%3A_Thin_Layer_Chromatography_(TLC)/2.3C%3A_The_Retention_Factor (Rf formula); hand calculation in content.mdx: 33 mm ÷ 0.55 = 60 mm"
    }
  ],
  "sources": [
    "LibreTexts, Lisa Nichols (Butte College), Organic Chemistry Lab Techniques, §2.3C The Retention Factor (CC BY-NC-ND 4.0): Rf = distance traveled by the compound ÷ distance traveled by the solvent front, both measured from the baseline, the 22 mm ÷ 40 mm = 0.55 example (Figure 2.14a), the repeated acetophenone runs (Figure 2.15), and that Rf values are approximate. https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_Lab_Techniques_(Nichols)/02%3A_Chromatography/2.03%3A_Thin_Layer_Chromatography_(TLC)/2.3C%3A_The_Retention_Factor (retrieved 2026-10-19)"
  ],
  "related": [
    "concentration",
    "dilution",
    "molarity",
    "percent-yield"
  ],
  "changelog": []
}