{
  "slug": "how-much-concrete-for-fence-post",
  "title": "How Much Concrete Do I Need for a Fence Post?",
  "heading": "How Much Concrete Do I Need for a Fence Post?",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/how-much-concrete-for-fence-post",
  "summary": "A standard 8-inch-diameter, 2-foot-deep post hole takes about 1.6 cubic feet (roughly one 50 lb bag) of concrete per post.",
  "description": "Fence post concrete volume depends on the hole diameter, hole depth, and how much of that volume the post itself displaces. The rule of thumb is to dig the hole 3x the post's width in diameter and set it about a third of the total post length (or below the frost line) into the ground. This tool computes the hole's cylindrical volume, subtracts the post's own volume, and converts the remaining concrete volume into cubic feet and the number of standard 50 lb or 80 lb bags you need per post and for your whole run of fence.",
  "formula": "Hole Volume = π × (Diameter/2)² × Depth. Concrete Volume = Hole Volume − Post Volume. Bags = Concrete Volume ÷ Yield per Bag.",
  "dateModified": "2026-09-06",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=how-much-concrete-for-fence-post",
  "inputs": [
    {
      "id": "diameter",
      "label": "Hole diameter",
      "kind": "number",
      "hint": null,
      "default": 8,
      "unit": "in",
      "min": 4,
      "max": 36
    },
    {
      "id": "depth",
      "label": "Hole depth",
      "kind": "number",
      "hint": null,
      "default": 24,
      "unit": "in",
      "min": 6,
      "max": 72
    },
    {
      "id": "postWidth",
      "label": "Post width (square post)",
      "kind": "number",
      "hint": null,
      "default": 4,
      "unit": "in",
      "min": 1,
      "max": 12
    },
    {
      "id": "postCount",
      "label": "Number of posts",
      "kind": "number",
      "hint": null,
      "default": 1,
      "unit": null,
      "min": 1,
      "max": 200
    },
    {
      "id": "bagYield",
      "label": "Bag size",
      "kind": "select",
      "hint": null,
      "default": "0.45",
      "options": [
        {
          "value": "0.6",
          "label": "50 lb bag (~0.375 cu ft)"
        },
        {
          "value": "0.45",
          "label": "60 lb bag (~0.45 cu ft)"
        },
        {
          "value": "0.6t",
          "label": "80 lb bag (~0.6 cu ft)"
        }
      ]
    }
  ],
  "outputs": [
    {
      "id": "totalBags",
      "label": "Total bags needed",
      "format": "number",
      "hint": null,
      "primary": true
    },
    {
      "id": "perPost",
      "label": "Concrete per post",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "bagsPerPost",
      "label": "Bags per post",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "totalVol",
      "label": "Total concrete volume (cu ft)",
      "format": "decimal",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Hole diameter: 8 in",
      "Hole depth: 24 in",
      "Post width (square post): 4 in",
      "Number of posts: 1",
      "Bag size: 60 lb bag (~0.45 cu ft)"
    ],
    "outputs": [
      "Total bags needed: 2",
      "Concrete per post: 0.48",
      "Bags per post: 1.06",
      "Total concrete volume (cu ft): 0.48"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter hole diameter (in).",
      "Enter hole depth (in).",
      "Enter post width (square post) (in).",
      "Enter number of posts.",
      "Enter bag size.",
      "Read your total bags 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": {
        "diameter": 5,
        "depth": 14,
        "postWidth": 2.4,
        "postCount": 1,
        "bagYield": "0.45"
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "diameter": 8,
        "depth": 24,
        "postWidth": 4,
        "postCount": 1,
        "bagYield": "0.45"
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "diameter": 13,
        "depth": 38,
        "postWidth": 6.4,
        "postCount": 2,
        "bagYield": "0.45"
      }
    }
  ],
  "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 much concrete do I need for a fence post?",
      "a": "For a typical 8-inch-diameter, 24-inch-deep hole with a 4x4 post, you need about 1.4 cubic feet of concrete per post after subtracting the post's volume — roughly one 60 lb bag (0.45 cu ft yield rounds up to about 3 bags per 4 posts, or just over one 50 lb bag each)."
    },
    {
      "q": "Why subtract the post's volume?",
      "a": "The post occupies space inside the hole that concrete would otherwise fill. For thick posts (6x6) this can shave 10-15% off the concrete needed versus assuming the hole is empty."
    },
    {
      "q": "How deep should a fence post hole be?",
      "a": "General guidance is one-third of the post's above-ground height, or below your local frost line, whichever is deeper — commonly 24-36 inches for a 6-foot fence."
    },
    {
      "q": "Should I round up on bags?",
      "a": "Always round up to the next full bag per post and buy a couple extra for spillage and uneven hole bottoms — running short mid-pour on quick-set concrete is a bigger problem than a leftover bag."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/how-much-sod-do-i-need",
    "https://www.revenuelab.fyi/toolbox/how-many-pavers-do-i-need"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — How Much Concrete Do I Need for a Fence Post? (https://www.revenuelab.fyi/toolbox/how-much-concrete-for-fence-post)"
}