{
  "slug": "concrete-slab",
  "title": "Concrete Slab Calculator",
  "heading": "Concrete Slab Calculator",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/concrete-slab",
  "summary": "Cubic yards, bags, and delivered cost for a slab pour.",
  "description": "Ready-mix is sold by the cubic yard and short-load fees are brutal, so it pays to order slightly over rather than run out mid-pour. This gives you volume, bag counts if you are mixing on site, and an estimated delivered cost.",
  "formula": "Volume (yd³) = Length × Width × Thickness (ft) ÷ 27, plus a waste allowance.",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=concrete-slab",
  "inputs": [
    {
      "id": "length",
      "label": "Length",
      "kind": "number",
      "hint": null,
      "default": 20,
      "unit": "ft",
      "min": 0,
      "max": null
    },
    {
      "id": "width",
      "label": "Width",
      "kind": "number",
      "hint": null,
      "default": 12,
      "unit": "ft",
      "min": 0,
      "max": null
    },
    {
      "id": "thickness",
      "label": "Thickness",
      "kind": "number",
      "hint": null,
      "default": 4,
      "unit": "in",
      "min": 1,
      "max": 24
    },
    {
      "id": "price",
      "label": "Ready-mix price",
      "kind": "number",
      "hint": null,
      "default": 165,
      "unit": "$/yd³",
      "min": 0,
      "max": null
    },
    {
      "id": "waste",
      "label": "Waste allowance",
      "kind": "number",
      "hint": "Cuts, breakage, and mistakes. 10% is standard.",
      "default": 10,
      "unit": "%",
      "min": 0,
      "max": 40
    }
  ],
  "outputs": [
    {
      "id": "yards",
      "label": "Concrete needed",
      "format": "decimal",
      "hint": null,
      "primary": true
    },
    {
      "id": "cost",
      "label": "Estimated ready-mix cost",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "bags60",
      "label": "60 lb bags (if mixing)",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "bags80",
      "label": "80 lb bags (if mixing)",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "area",
      "label": "Slab area (sq ft)",
      "format": "number",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Length: 20 ft",
      "Width: 12 ft",
      "Thickness: 4 in",
      "Ready-mix price: 165 $/yd³",
      "Waste allowance: 10 %"
    ],
    "outputs": [
      "Concrete needed: 3.26",
      "Estimated ready-mix cost: $537.78",
      "60 lb bags (if mixing): 196",
      "80 lb bags (if mixing): 147",
      "Slab area (sq ft): 240"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter length (ft).",
      "Enter width (ft).",
      "Enter thickness (in).",
      "Enter ready-mix price ($/yd³).",
      "Enter waste allowance (%) — Cuts, breakage, and mistakes. 10% is standard..",
      "Read your concrete 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": {
        "length": 12,
        "width": 7,
        "thickness": 2.4,
        "price": 100,
        "waste": 6
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "length": 20,
        "width": 12,
        "thickness": 4,
        "price": 165,
        "waste": 10
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "length": 32,
        "width": 19,
        "thickness": 6.4,
        "price": 265,
        "waste": 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": "How does the concrete slab calculator work?",
      "a": "Ready-mix is sold by the cubic yard and short-load fees are brutal, so it pays to order slightly over rather than run out mid-pour. This gives you volume, bag counts if you are mixing on site, and an estimated delivered cost. The underlying maths is: Volume (yd³) = Length × Width × Thickness (ft) ÷ 27, plus a waste allowance."
    },
    {
      "q": "What do I need to enter?",
      "a": "5 values: length, width, thickness, ready-mix price, and waste allowance. 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 concrete needed result mean?",
      "a": "It is returned as a decimal 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/concrete-footing",
    "https://www.revenuelab.fyi/toolbox/rebar",
    "https://www.revenuelab.fyi/toolbox/gravel"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Concrete Slab Calculator (https://www.revenuelab.fyi/toolbox/concrete-slab)"
}