{
  "id": "epoxy",
  "version": "e3b18783a7dd",
  "status": "published",
  "name": "Epoxy Calculator",
  "question": "How much epoxy do I need?",
  "summary": "Computes the volume of epoxy resin to coat or pour a rectangular or round surface to a thickness, with extra for waste, in gallons, fluid ounces and litres, and how much resin and hardener to mix.",
  "category": "construction",
  "subcategory": "materials",
  "url": "https://www.acalculator.org/construction/epoxy-calculator",
  "markdown": "https://www.acalculator.org/construction/epoxy-calculator.md",
  "kind": "function",
  "method": "Volume = length × width (or π × diameter² ÷ 4) × thickness × (1 + extra ÷ 100); resin = volume × a ÷ (a + b); hardener = volume × b ÷ (a + b), for an a:b mix by volume.",
  "assumptions": [
    "The epoxy spreads to an even thickness over the whole surface; a rough or porous surface soaks up more.",
    "Extra for waste is 10% by default, for drips over the edges and resin left in the mixing cup.",
    "The mix ratio is by volume. For an epoxy mixed by weight, use the maker’s weights instead."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "shape": {
        "title": "Shape",
        "description": "Whether the surface is a rectangle or a circle.",
        "type": "string",
        "enum": [
          "rect",
          "circle"
        ]
      },
      "l": {
        "title": "Length",
        "description": "The length of the surface.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "exclusiveMinimum": 0,
        "maximum": 1000
      },
      "w": {
        "title": "Width",
        "description": "The width of the surface.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "exclusiveMinimum": 0,
        "maximum": 1000
      },
      "d": {
        "title": "Diameter",
        "description": "The diameter of a round surface.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "exclusiveMinimum": 0,
        "maximum": 1000
      },
      "t": {
        "title": "Thickness",
        "description": "How thick the epoxy layer is: the coat or the pour depth.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "exclusiveMinimum": 0,
        "maximum": 1
      },
      "extra": {
        "title": "Extra for waste",
        "description": "Epoxy to add on top of the layer volume, in percent, for drips over the edges and resin left in the cup.",
        "type": "number",
        "x-unit": "percent",
        "minimum": 0,
        "maximum": 100
      },
      "a": {
        "title": "Resin parts",
        "description": "The resin part of the mix ratio by volume: 1 for a 1:1 epoxy, 2 for 2:1.",
        "type": "number",
        "exclusiveMinimum": 0,
        "maximum": 100
      },
      "b": {
        "title": "Hardener parts",
        "description": "The hardener part of the mix ratio by volume, usually 1.",
        "type": "number",
        "exclusiveMinimum": 0,
        "maximum": 100
      }
    }
  },
  "outputs": {
    "gallons": {
      "label": "US gallons",
      "description": "The epoxy to mix, in US gallons (231 in³ each).",
      "format": "number"
    },
    "fluidOunces": {
      "label": "Fluid ounces",
      "description": "The epoxy to mix, in US fluid ounces (128 to the gallon).",
      "format": "number"
    },
    "liters": {
      "label": "Litres",
      "description": "The epoxy to mix, in litres.",
      "format": "number"
    },
    "resinOunces": {
      "label": "Resin, fluid ounces",
      "description": "The resin part of the mix, in US fluid ounces.",
      "format": "number"
    },
    "hardenerOunces": {
      "label": "Hardener, fluid ounces",
      "description": "The hardener part of the mix, in US fluid ounces.",
      "format": "number"
    },
    "resinMl": {
      "label": "Resin, millilitres",
      "description": "The resin part of the mix, in millilitres.",
      "format": "number"
    },
    "hardenerMl": {
      "label": "Hardener, millilitres",
      "description": "The hardener part of the mix, in millilitres.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "shape": "rect",
      "l": 1.2192,
      "w": 0.6096,
      "d": 0.9144000000000001,
      "t": 0.003175,
      "extra": 10,
      "a": 1,
      "b": 1
    },
    "outputs": {
      "gallons": 0.6857142857142857,
      "fluidOunces": 87.77142857142857,
      "liters": 2.5957109376,
      "resinOunces": 43.885714285714286,
      "hardenerOunces": 43.885714285714286,
      "resinMl": 1297.8554688,
      "hardenerMl": 1297.8554688
    },
    "text": "Mix 0.686 gal (2.596 L) of epoxy: 43.9 fl oz of resin and 43.9 fl oz of hardener."
  },
  "examples": [
    {
      "given": {
        "shape": "rect",
        "l": 1.2192,
        "w": 0.6096,
        "t": 0.003175,
        "extra": 10,
        "a": 1,
        "b": 1
      },
      "expect": {
        "gallons": 0.6857142857142857,
        "fluidOunces": 87.77142857142857,
        "liters": 2.5957109376,
        "resinOunces": 43.885714285714286,
        "resinMl": 1297.8554688
      },
      "source": "NIST Handbook 44, Appendix C (1 US gallon = 231 in³ = 128 fl oz = 3.785411784 L); hand calculation in content.mdx: 48 × 24 × 0.125 = 144 in³ × 1.1 = 158.4 in³ ÷ 231 = 0.686 gal"
    },
    {
      "given": {
        "shape": "rect",
        "l": 1,
        "w": 0.5,
        "t": 0.002,
        "extra": 0,
        "a": 2,
        "b": 1
      },
      "expect": {
        "liters": 1,
        "resinMl": 666.6666666666666,
        "hardenerMl": 333.3333333333333,
        "gallons": 0.2641720523581484
      },
      "source": "NIST Handbook 44, Appendix C (1 L = 0.001 m³); hand calculation in content.mdx: 100 × 50 × 0.2 = 1,000 cm³ = 1 L; 2:1 gives 666.7 mL resin and 333.3 mL hardener"
    },
    {
      "given": {
        "shape": "circle",
        "d": 0.9144000000000001,
        "t": 0.00635,
        "extra": 0,
        "a": 1,
        "b": 1
      },
      "expect": {
        "gallons": 1.101597423986031
      },
      "source": "Cylinder volume π × d² ÷ 4 × thickness (OpenStax, Prealgebra 2e, §9.6); NIST Handbook 44, Appendix C (1 gal = 231 in³); hand calculation in content.mdx: π × 36² ÷ 4 × 0.25 = 254.47 in³ ÷ 231 = 1.102 gal"
    }
  ],
  "sources": [
    "NIST Handbook 44 (2024), Appendix C, General Tables of Units of Measurement: 1 US gallon = 231 in³ = 128 US fl oz = 3.785411784 L; 1 L = 1,000 mL = 0.001 m³. https://www.nist.gov/pml/owm/nist-handbook-44-current-edition",
    "OpenStax, Prealgebra 2e, §9.6 Solve Geometry Applications: Volume and Surface Area (volume of a rectangular solid and of a cylinder). https://openstax.org/books/prealgebra-2e/pages/9-6-solve-geometry-applications-volume-and-surface-area"
  ],
  "related": [
    "concrete",
    "square-footage"
  ],
  "changelog": [
    {
      "date": "2026-09-30",
      "note": "Metric heads the result with the epoxy in litres; the answer names litres and millilitres."
    }
  ]
}