{
  "slug": "20x20-concrete-slab-calculator",
  "title": "20x20 Concrete Slab Calculator",
  "heading": "20x20 Concrete Slab Calculator",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/20x20-concrete-slab-calculator",
  "summary": "Yardage and cost for a 20x20 garage pad or large patio, pre-filled at 4 inches thick.",
  "description": "20x20 is the classic single-car garage or large-patio footprint — 400 square feet of slab. Because that's enough concrete to matter financially, this calculator defaults to 4 inches thick but lets you bump it to 5 or 6 inches if the slab needs to carry a vehicle, then converts the volume into ready-mix cubic yards and a total cost so you can get an accurate number before calling a supplier.",
  "formula": "Cubic Yards = (Length × Width × Thickness in inches ÷ 12) ÷ 27 × (1 + Waste%). Cost = Cubic Yards × Price per Yard.",
  "dateModified": "2026-09-06",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=20x20-concrete-slab-calculator",
  "inputs": [
    {
      "id": "length",
      "label": "Slab length",
      "kind": "number",
      "hint": null,
      "default": 20,
      "unit": "ft",
      "min": 1,
      "max": null
    },
    {
      "id": "width",
      "label": "Slab width",
      "kind": "number",
      "hint": null,
      "default": 20,
      "unit": "ft",
      "min": 1,
      "max": null
    },
    {
      "id": "thickness",
      "label": "Thickness",
      "kind": "number",
      "hint": null,
      "default": 4,
      "unit": "in",
      "min": 2,
      "max": 12
    },
    {
      "id": "waste",
      "label": "Waste factor",
      "kind": "number",
      "hint": null,
      "default": 10,
      "unit": "%",
      "min": 0,
      "max": 30
    },
    {
      "id": "pricePerYard",
      "label": "Ready-mix price per cubic yard",
      "kind": "number",
      "hint": null,
      "default": 150,
      "unit": "$",
      "min": 0,
      "max": null
    }
  ],
  "outputs": [
    {
      "id": "cubicYards",
      "label": "Ready-mix needed",
      "format": "decimal",
      "hint": null,
      "primary": true
    },
    {
      "id": "bags",
      "label": "80-lb bags (DIY mix)",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "cost",
      "label": "Estimated concrete cost",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "cubicFeet",
      "label": "Total cubic feet",
      "format": "decimal",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Slab length: 20 ft",
      "Slab width: 20 ft",
      "Thickness: 4 in",
      "Waste factor: 10 %",
      "Ready-mix price per cubic yard: 150 $"
    ],
    "outputs": [
      "Ready-mix needed: 5.43",
      "80-lb bags (DIY mix): 244",
      "Estimated concrete cost: $815",
      "Total cubic feet: 133.3"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter slab length (ft).",
      "Enter slab width (ft).",
      "Enter thickness (in).",
      "Enter waste factor (%).",
      "Enter ready-mix price per cubic yard ($).",
      "Read your ready-mix 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": 12,
        "thickness": 2.4,
        "waste": 6,
        "pricePerYard": 90
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "length": 20,
        "width": 20,
        "thickness": 4,
        "waste": 10,
        "pricePerYard": 150
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "length": 32,
        "width": 32,
        "thickness": 6.4,
        "waste": 16,
        "pricePerYard": 240
      }
    }
  ],
  "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": "Is 20x20 big enough for a two-car garage?",
      "a": "It's tight — most two-car garages run closer to 20x24 or 24x24. 20x20 comfortably fits one large vehicle plus storage, or works well as a detached garage pad."
    },
    {
      "q": "How thick should a 20x20 garage slab be?",
      "a": "5-6 inches is standard for a vehicle-bearing slab, versus 4 inches for foot-traffic-only patios. Thicker slabs use proportionally more concrete, so adjust the thickness field before ordering."
    },
    {
      "q": "How much does a 20x20 slab typically cost installed?",
      "a": "Materials alone (concrete plus mesh/rebar and forms) commonly run several thousand dollars; labor for excavation, forming, and finishing often equals or exceeds material cost, so use this tool's material number as a starting point, not a full turnkey quote."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/24x24-garage-calculator",
    "https://www.revenuelab.fyi/toolbox/12x12-concrete-slab-calculator"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — 20x20 Concrete Slab Calculator (https://www.revenuelab.fyi/toolbox/20x20-concrete-slab-calculator)"
}