{
    "name": "Electrical Conduit Fill Calculator",
    "url": "https://calculators.geekmidst.com/calculators/electrical-conduit-fill-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/electrical-conduit-fill-calculator.md",
    "category": "Construction",
    "description": "Check conduit fill from the conduit’s internal diameter and the conductor diameters, against a fill limit you take from your wiring code.",
    "summary": "Conduit fill is the total cross-section of the conductors divided by the conduit’s internal cross-section. Enter the internal diameter and the fill limit from the tables you work to.",
    "also_called": [
        "Conduit sizing calculator",
        "Wire fill calculator"
    ],
    "applies_to": "Worldwide",
    "last_updated": "2026-10-29",
    "computation": "Results are computed in the visitor’s browser on the HTML page. This API describes the calculator; it does not compute results.",
    "inputs": [
        {
            "name": "conduit_id",
            "label": "Conduit internal diameter",
            "type": "number",
            "default": "25",
            "unit": "mm"
        },
        {
            "name": "count1",
            "label": "Number of conductors",
            "type": "number",
            "default": "6"
        },
        {
            "name": "od1",
            "label": "Conductor outside diameter (with insulation)",
            "type": "number",
            "default": "4",
            "unit": "mm"
        },
        {
            "name": "count2",
            "label": "Second conductor group: number",
            "type": "number",
            "default": "",
            "optional": true
        },
        {
            "name": "od2",
            "label": "Second conductor group: diameter",
            "type": "number",
            "default": "",
            "unit": "mm",
            "optional": true
        },
        {
            "name": "limit",
            "label": "Allowable fill",
            "type": "number",
            "default": "40",
            "unit": "%"
        }
    ],
    "outputs": [
        {
            "key": "fill_pct",
            "label": "Conduit fill",
            "format": "percent"
        },
        {
            "key": "status",
            "label": "Against your limit",
            "format": "text"
        },
        {
            "key": "conductor_area",
            "label": "Conductor cross-section",
            "format": "number"
        },
        {
            "key": "conduit_area",
            "label": "Conduit internal cross-section",
            "format": "number"
        },
        {
            "key": "allowed_area",
            "label": "Allowed conductor area",
            "format": "number"
        },
        {
            "key": "max_same",
            "label": "Maximum conductors of the first size",
            "format": "integer"
        }
    ],
    "formula": {
        "text": "Fill = Σ n × π d² ÷ 4 ÷ (π D² ÷ 4) × 100 = Σ n d² ÷ D² × 100",
        "variables": {
            "n, d": "number and outside diameter of each conductor group",
            "D": "conduit internal diameter"
        }
    },
    "worked_example": {
        "inputs": {
            "conduit_id": "25",
            "count1": "6",
            "od1": "4",
            "count2": "",
            "od2": "",
            "limit": "40"
        },
        "steps": [
            "Fill = 6 × 4² ÷ 25² = 96 ÷ 625 = 15.36%.",
            "Conduit area = π × 25² ÷ 4 = 490.87 mm²; 40% of it is 196.35 mm².",
            "Each conductor is 12.57 mm², so up to 15 fit within 40%."
        ],
        "result": "Six 4 mm conductors fill a 25 mm-bore conduit to 15.36%, well within a 40% limit."
    },
    "interpretation": "Fill limits keep conductors from being damaged when pulled and allow heat to escape. Grouped circuits may also need current derating, which this calculator does not check.",
    "assumptions": [
        "Conductors are round; their overall outside diameter is used."
    ],
    "limitations": [
        "Fill limits depend on the number of conductors, conduit type and code; enter the one that applies.",
        "Jamming, bends and pull tension are not checked."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "Why does the limit change with the number of conductors?",
            "answer": "Many codes allow a higher fill for a single conductor than for several, because several round conductors pack less efficiently and are harder to pull."
        },
        {
            "question": "Can I use the nominal conduit size?",
            "answer": "No. Use the internal diameter for your conduit type; it differs between materials with the same trade size."
        }
    ],
    "sources": [],
    "related": [
        {
            "name": "Cable Tray Fill Calculator",
            "url": "https://calculators.geekmidst.com/calculators/cable-tray-fill-calculator"
        },
        {
            "name": "Percentage Calculator",
            "url": "https://calculators.geekmidst.com/calculators/percentage-calculator"
        },
        {
            "name": "Plumbing Pipe Flow Calculator",
            "url": "https://calculators.geekmidst.com/calculators/plumbing-pipe-flow-calculator"
        }
    ],
    "disclaimer": "Quantities are estimates. Confirm requirements with your engineer or supplier before ordering materials.",
    "publisher": "GM¹X CalcVerse"
}