{
  "address": "d5227d139cd4fb6a8288cecd76da4570",
  "category": "other",
  "question": "How many liters of paint are needed for a 4m by 3m room with 2.5m walls, 3 square meters of openings, 2 coat(s), and paint that covers 10 square meters per liter?",
  "answer": "6.40 liters",
  "askedBy": {
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  "madeAt": "2026-09-30T22:39:30.722Z",
  "validUntil": null,
  "validityClass": "forever",
  "sources": [
    {
      "label": "Paint Calculator: How Much Paint Do I Need?",
      "url": "https://www.thisoldhouse.com/painting/21097077/how-much-paint-do-i-need"
    }
  ],
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  "unpublishedAt": null,
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  "answerMethod": "method",
  "unsourced": false,
  "source": {
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    "value": "https://www.thisoldhouse.com/painting/21097077/how-much-paint-do-i-need",
    "retrieved_utc": "2026-09-30T22:29:13Z"
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  "cardContractVersion": "card_contract/1",
  "deck_id": "method-deck",
  "deck_title": "Method Deck",
  "method": {
    "name": "Paint needed for a rectangular room",
    "version": "1",
    "source_url_or_file": "methods/rectangle-room-paint-coverage.cjs",
    "sha256_of_method_file": "4d642f23183d8c4202811506044cac63b8fd4d6cca946acb0242d9284d6da0b7"
  },
  "receipt": {
    "inSubstrate": false,
    "local": true,
    "modelCallsAtMint": 0,
    "tokensAtMint": 0
  },
  "method_deck": {
    "inputs": [
      {
        "name": "length",
        "type": "number",
        "unit": "meters",
        "required": true,
        "description": "Room length.",
        "min": 0
      },
      {
        "name": "width",
        "type": "number",
        "unit": "meters",
        "required": true,
        "description": "Room width.",
        "min": 0
      },
      {
        "name": "height",
        "type": "number",
        "unit": "meters",
        "required": true,
        "description": "Wall height.",
        "min": 0
      },
      {
        "name": "openings_area",
        "type": "number",
        "unit": "square meters",
        "required": true,
        "description": "Total area of doors and windows to subtract.",
        "min": 0
      },
      {
        "name": "coats",
        "type": "integer",
        "unit": "coats",
        "required": true,
        "description": "Number of coats of paint to apply.",
        "min": 1
      },
      {
        "name": "coverage_per_liter",
        "type": "number",
        "unit": "square meters per liter",
        "required": true,
        "description": "Manufacturer-stated coverage of the paint, one coat.",
        "min": 0
      }
    ],
    "outputs": [
      {
        "name": "wall_area",
        "unit": "square meters",
        "description": "Net paintable wall area, one coat."
      },
      {
        "name": "paint_needed_liters",
        "unit": "liters",
        "description": "Total paint needed for all coats."
      }
    ],
    "steps": [
      "Wall perimeter = 2 * (length + width).",
      "Gross wall area = perimeter * height.",
      "Net wall area = gross wall area - openings_area.",
      "Paint needed (liters) = net wall area * coats / coverage_per_liter.",
      "Round both outputs to 2 decimals."
    ],
    "constants": [],
    "examples": [
      {
        "name": "worked example",
        "inputs": {
          "length": 4,
          "width": 3,
          "height": 2.5,
          "openings_area": 3,
          "coats": 2,
          "coverage_per_liter": 10
        },
        "expected": {
          "answer": "6.40 liters"
        },
        "check": "By hand: perimeter=2*(4+3)=14 m; gross wall area=14*2.5=35 sq m; net area=35-3=32 sq m; paint=32*2/10=6.4 liters."
      },
      {
        "name": "test vector: one coat",
        "inputs": {
          "length": 5,
          "width": 5,
          "height": 3,
          "openings_area": 4,
          "coats": 1,
          "coverage_per_liter": 8
        },
        "expected": {
          "answer": "7.00 liters"
        },
        "check": "By hand: perimeter=2*(5+5)=20 m; gross wall area=20*3=60 sq m; net area=60-4=56 sq m; paint=56*1/8=7.00 liters."
      }
    ],
    "disclaimer": null,
    "deck_category": "geometry"
  },
  "status": "minted",
  "kind": "method",
  "provenanceClass": "own_question",
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    "chain": [
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          "value": "https://www.thisoldhouse.com/painting/21097077/how-much-paint-do-i-need",
          "retrieved_utc": "2026-09-30T22:29:13Z"
        },
        "sha256": "4e4a99768e6361640e3251cbae0a13d15c8c3e1a4858471d5601b6e41aca7b10",
        "supersedes": null,
        "added_utc": "2026-09-30T22:39:30.722Z",
        "added_by": "method:Paint needed for a rectangular room",
        "why": "the method that computed this answer",
        "check": null,
        "status_label": "pending",
        "signature": null
      }
    ]
  }
}