{
  "slug": "btu-sizing",
  "title": "BTU Sizing Calculator",
  "heading": "Air Conditioner & Heater BTU Calculator",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/btu-sizing",
  "summary": "How many BTUs a room needs based on size and conditions.",
  "description": "The 20 BTU per square foot baseline shifts with ceiling height, sun exposure, insulation, and occupancy. Oversizing short-cycles the unit and leaves the room humid.",
  "formula": "BTU = Square feet × 20, adjusted for sun, ceiling height, insulation, and occupants.",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=btu-sizing",
  "inputs": [
    {
      "id": "sqft",
      "label": "Room area",
      "kind": "number",
      "hint": null,
      "default": 400,
      "unit": "sq ft",
      "min": 20,
      "max": null
    },
    {
      "id": "ceiling",
      "label": "Ceiling height",
      "kind": "number",
      "hint": null,
      "default": 8,
      "unit": "ft",
      "min": 6,
      "max": 20
    },
    {
      "id": "sun",
      "label": "Sun exposure",
      "kind": "select",
      "hint": null,
      "default": "average",
      "options": [
        {
          "value": "shaded",
          "label": "Heavily shaded"
        },
        {
          "value": "average",
          "label": "Average"
        },
        {
          "value": "sunny",
          "label": "Very sunny"
        }
      ]
    },
    {
      "id": "insulation",
      "label": "Insulation",
      "kind": "select",
      "hint": null,
      "default": "average",
      "options": [
        {
          "value": "poor",
          "label": "Poor"
        },
        {
          "value": "average",
          "label": "Average"
        },
        {
          "value": "good",
          "label": "Well insulated"
        }
      ]
    },
    {
      "id": "occupants",
      "label": "Regular occupants",
      "kind": "number",
      "hint": null,
      "default": 2,
      "unit": null,
      "min": 1,
      "max": 20
    },
    {
      "id": "kitchen",
      "label": "Is it a kitchen?",
      "kind": "select",
      "hint": null,
      "default": "no",
      "options": [
        {
          "value": "no",
          "label": "No"
        },
        {
          "value": "yes",
          "label": "Yes (+4,000 BTU)"
        }
      ]
    }
  ],
  "outputs": [
    {
      "id": "recommended",
      "label": "Recommended cooling capacity (BTU)",
      "format": "number",
      "hint": null,
      "primary": true
    },
    {
      "id": "tons",
      "label": "Tons of cooling",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "heating",
      "label": "Heating BTU estimate",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "watts",
      "label": "Equivalent electric watts",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "volume",
      "label": "Room volume (cu ft)",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "btu",
      "label": "Raw calculated BTU",
      "format": "decimal",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Room area: 400 sq ft",
      "Ceiling height: 8 ft",
      "Sun exposure: Average",
      "Insulation: Average",
      "Regular occupants: 2",
      "Is it a kitchen?: No"
    ],
    "outputs": [
      "Recommended cooling capacity (BTU): 8,000",
      "Tons of cooling: 0.67",
      "Heating BTU estimate: 14,000",
      "Equivalent electric watts: 2,345",
      "Room volume (cu ft): 3,200",
      "Raw calculated BTU: 8,000"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter room area (sq ft).",
      "Enter ceiling height (ft).",
      "Enter sun exposure.",
      "Enter insulation.",
      "Enter regular occupants.",
      "Enter is it a kitchen?.",
      "Read your recommended cooling capacity (btu) 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": {
        "sqft": 240,
        "ceiling": 6,
        "sun": "average",
        "insulation": "average",
        "occupants": 1,
        "kitchen": "no"
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "sqft": 400,
        "ceiling": 8,
        "sun": "average",
        "insulation": "average",
        "occupants": 2,
        "kitchen": "no"
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "sqft": 640,
        "ceiling": 12.8,
        "sun": "average",
        "insulation": "average",
        "occupants": 3,
        "kitchen": "no"
      }
    }
  ],
  "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": "How does the air conditioner & heater btu calculator work?",
      "a": "The 20 BTU per square foot baseline shifts with ceiling height, sun exposure, insulation, and occupancy. Oversizing short-cycles the unit and leaves the room humid. The underlying maths is: BTU = Square feet × 20, adjusted for sun, ceiling height, insulation, and occupants."
    },
    {
      "q": "What do I need to enter?",
      "a": "6 values: room area, ceiling height, sun exposure, insulation, regular occupants, and is it a kitchen?. Each field starts with a sensible default, so you can change one number at a time and watch the result move."
    },
    {
      "q": "What does the recommended cooling capacity (btu) result mean?",
      "a": "It is returned as a whole number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds."
    },
    {
      "q": "Is this calculator free, and do I need an account?",
      "a": "Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser."
    },
    {
      "q": "How accurate is the result?",
      "a": "It applies the standard formula exactly, so the arithmetic is precise. Estimates assume standard, average conditions — local rules, pricing, and materials vary."
    },
    {
      "q": "Who is this tool for?",
      "a": "It's built for anyone doing everyday planning maths — a quick estimate that would otherwise need four browser tabs and a calculator app."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/hvac-run-cost",
    "https://www.revenuelab.fyi/toolbox/electricity-cost"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — BTU Sizing Calculator (https://www.revenuelab.fyi/toolbox/btu-sizing)"
}