{
  "slug": "insulation-batts-calculator",
  "title": "Insulation Batts Calculator",
  "heading": "Insulation Batts Calculator",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/insulation-batts-calculator",
  "summary": "Figure out how many fiberglass or mineral wool batts you need for a wall or attic area.",
  "description": "Insulation batts are sold in standard sizes — commonly 15\" or 23\" wide by 93\" or 96\" long — sized to fit snugly between studs spaced 16 or 24 inches on center, and each batt's package states its coverage in square feet, typically around 40-50 sq ft per pack of multiple batts or per individual batt depending on thickness and R-value. This calculator takes your total area to insulate (wall square footage or attic floor square footage) and divides it by the coverage per batt or per pack, rounding up since batts can't be meaningfully spliced to cover a fractional remaining bay without leaving a gap. It also applies a small waste factor to account for batts cut around electrical boxes, plumbing runs, and non-standard stud bays at corners and ends of walls, which happen on nearly every real installation. Getting the R-value right for your climate zone matters as much as the square footage — R-13 to R-15 batts are standard for 2x4 walls, R-19 to R-21 for 2x6 walls, and attics often call for R-38 to R-60 depending on region, so always confirm your local code's minimum before buying based on square footage alone.",
  "formula": "Batts = ceil((Area ÷ Coverage per Batt) × (1 + Waste%)).",
  "dateModified": "2026-09-06",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=insulation-batts-calculator",
  "inputs": [
    {
      "id": "area",
      "label": "Area to insulate",
      "kind": "number",
      "hint": null,
      "default": 600,
      "unit": "sq ft",
      "min": 10,
      "max": null
    },
    {
      "id": "coveragePerBatt",
      "label": "Coverage per batt",
      "kind": "number",
      "hint": null,
      "default": 21,
      "unit": "sq ft",
      "min": 5,
      "max": 50
    },
    {
      "id": "wastePct",
      "label": "Waste factor",
      "kind": "number",
      "hint": null,
      "default": 10,
      "unit": "%",
      "min": 0,
      "max": 25
    }
  ],
  "outputs": [
    {
      "id": "batts",
      "label": "Batts needed",
      "format": "number",
      "hint": null,
      "primary": true
    },
    {
      "id": "area",
      "label": "Area to insulate",
      "format": "number",
      "hint": "sq ft",
      "primary": false
    },
    {
      "id": "rawBatts",
      "label": "Exact batts before rounding",
      "format": "decimal",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Area to insulate: 600 sq ft",
      "Coverage per batt: 21 sq ft",
      "Waste factor: 10 %"
    ],
    "outputs": [
      "Batts needed: 32",
      "Area to insulate: 600",
      "Exact batts before rounding: 31.43"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter area to insulate (sq ft).",
      "Enter coverage per batt (sq ft).",
      "Enter waste factor (%).",
      "Read your batts needed on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "area": 360,
        "coveragePerBatt": 13,
        "wastePct": 6
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "area": 600,
        "coveragePerBatt": 21,
        "wastePct": 10
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "area": 960,
        "coveragePerBatt": 34,
        "wastePct": 16
      }
    }
  ],
  "limitations": [
    "Estimates assume standard, average conditions — local rules, pricing, and materials vary.",
    "Results are rounded for readability; add a buffer before ordering, booking, or committing.",
    "Double-check anything with a real cost attached against a local quote."
  ],
  "faq": [
    {
      "q": "What R-value do I need for exterior walls?",
      "a": "Most codes call for R-13 to R-15 in 2x4 walls and R-19 to R-21 in 2x6 walls, though colder climate zones may require higher values, so check your local energy code before buying."
    },
    {
      "q": "Should I buy faced or unfaced batts?",
      "a": "Faced batts (with a paper or foil vapor barrier) are used on exterior walls and ceilings where a vapor barrier is needed facing the warm-in-winter side; unfaced batts are used for interior sound-dampening walls or when adding a layer over existing insulation."
    },
    {
      "q": "How much area does one batt cover?",
      "a": "A single standard batt (15\" x 93\") covers roughly 19-20 sq ft, but packages often bundle multiple batts and list total pack coverage, so always check the specific product's printed coverage rather than assuming a universal number."
    },
    {
      "q": "What waste factor should I use for batt insulation?",
      "a": "10% is typical for standard stud spacing; increase to 15-20% for older homes with irregular framing, many electrical boxes, or non-standard stud spacing that requires more cutting and fitting."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/blown-in-insulation-bags-calculator",
    "https://www.revenuelab.fyi/toolbox/drywall-sheets-calculator",
    "https://www.revenuelab.fyi/toolbox/joint-compound-calculator"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Insulation Batts Calculator (https://www.revenuelab.fyi/toolbox/insulation-batts-calculator)"
}