{
  "tool": "wallpaper",
  "version": "1.0.0",
  "inputs": {
    "mode": "room",
    "room_length_cm": 400,
    "room_width_cm": 300,
    "wall_width_cm": 350,
    "wall_height_cm": 240,
    "roll_length_cm": 1005,
    "roll_width_cm": 53,
    "pattern_repeat_cm": 0,
    "match": "free",
    "doors": 1,
    "trim_cm": 10,
    "spare_rolls": 1
  },
  "answer": {
    "rolls": 8,
    "rolls_without_spare": 7,
    "spare_rolls": 1,
    "drops_needed": 26,
    "drops_per_roll": 4,
    "cuts": {
      "wall_width_cm": 1400,
      "drop_cut_cm": 250,
      "drop_used_cm": 250,
      "offcut_per_roll_cm": 5,
      "wall_area_m2": 33.6,
      "doors_saved_drops": 1
    }
  },
  "summary": "To paper a 4 m × 3 m room with 240 cm walls you need 8 rolls of 10.05 m × 53 cm paper: 26 drops, 4 from each roll, plus 1 spare.",
  "working": [
    "Walls round the room: 2 × (4 m + 3 m) = 14 m",
    "14 m ÷ 53 cm roll width = 26.4, so 27 drops",
    "Less 1 drop for 1 door: 26 drops",
    "Each drop: 240 cm + 10 cm trim = 250 cm",
    "10.05 m roll ÷ 250 cm = 4 drops per roll",
    "26 drops ÷ 4 = 7 rolls, plus 1 spare = 8"
  ],
  "notes": [
    "Buy every roll with the same batch number, the spare too: a later batch can differ in colour.",
    "Windows save no paper: the pieces above and below them use most of a drop."
  ],
  "sources": [
    {
      "label": "B&Q, GoodHome Kerria wallpaper (10,050 × 530 mm, 64 cm straight match)",
      "url": "https://www.diy.com/departments/goodhome-kerria-white-leaves-wallpaper/3663602560562_BQ.prd",
      "checked": "2026-10-31"
    },
    {
      "label": "Which?, How to wallpaper (check every roll is from the same batch; buy an extra roll or two)",
      "url": "https://www.which.co.uk/reviews/decorating-and-diy/article/how-to-wallpaper-a5vrr3F24tdk",
      "checked": "2026-10-31"
    },
    {
      "label": "PracticalDIY, Estimating the number of rolls (same batch or lot number; a couple of extra rolls for a large repeat)",
      "url": "https://www.practicaldiy.com/decorating/wallpaper/wallpaper_quantity.php",
      "checked": "2026-10-31"
    },
    {
      "label": "Graham & Brown, How to measure for wallpaper (allow an extra 10% for waste)",
      "url": "https://www.grahambrown.com/uk/how-to/measure-your-room/",
      "checked": "2026-10-31"
    },
    {
      "label": "Howarth Timber (Green, 14 Sep 2026), UK door sizes",
      "url": "https://www.howarth-timber.co.uk/inspiration-advice/uk-door-sizes",
      "checked": "2026-10-31"
    }
  ],
  "page_url": "https://snuug.app/tools/wallpaper",
  "snuug": "Snuug is an iPhone app that rebuilds your room in 3D, to within about 3% of its real size, so you can redesign it and see what fits before you buy a thing. Not yet on the App Store (31 October 2026)."
}