{
    "name": "Farm Pond Volume Calculator",
    "url": "https://calculators.geekmidst.com/calculators/farm-pond-volume-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/farm-pond-volume-calculator.md",
    "category": "Agriculture",
    "description": "Find the water a dug farm pond holds from its top length and width, depth and side slope, in cubic metres, litres, cubic feet and US gallons.",
    "summary": "A dug pond with sloping sides is an upside-down truncated pyramid. The prismoidal formula gives its exact volume from the top, middle and bottom areas.",
    "also_called": [
        "Dugout volume calculator",
        "Pond capacity 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": "unit",
            "label": "Dimensions in",
            "type": "segmented",
            "default": "m",
            "options": {
                "m": "Metres",
                "ft": "Feet"
            }
        },
        {
            "name": "top_length",
            "label": "Top length (at water level)",
            "type": "number",
            "default": "30"
        },
        {
            "name": "top_width",
            "label": "Top width (at water level)",
            "type": "number",
            "default": "20"
        },
        {
            "name": "depth",
            "label": "Water depth",
            "type": "number",
            "default": "3"
        },
        {
            "name": "slope",
            "label": "Side slope (horizontal : 1 vertical)",
            "type": "number",
            "default": "2"
        }
    ],
    "outputs": [
        {
            "key": "volume_m3",
            "label": "Pond volume",
            "format": "number"
        },
        {
            "key": "litres",
            "label": "Pond volume",
            "format": "number"
        },
        {
            "key": "us_gal",
            "label": "Pond volume (US gallons)",
            "format": "number"
        },
        {
            "key": "volume_ft3",
            "label": "Pond volume",
            "format": "number"
        },
        {
            "key": "bottom_length",
            "label": "Bottom length",
            "format": "number"
        },
        {
            "key": "bottom_width",
            "label": "Bottom width",
            "format": "number"
        }
    ],
    "formula": {
        "text": "Bottom = Top − 2·z·d;  V = d ÷ 6 × (A_top + 4·A_mid + A_bottom)",
        "variables": {
            "d": "water depth",
            "z": "side slope, horizontal per unit vertical",
            "A_top, A_bottom": "areas of the water surface and the floor",
            "A_mid": "area at half depth: (L − z·d)(W − z·d)"
        }
    },
    "worked_example": {
        "inputs": {
            "unit": "m",
            "top_length": "30",
            "top_width": "20",
            "depth": "3",
            "slope": "2"
        },
        "steps": [
            "Bottom = (30 − 2×2×3) × (20 − 12) = 18 × 8 = 144 m².",
            "Mid-depth = (30 − 6) × (20 − 6) = 24 × 14 = 336 m²; top = 600 m².",
            "V = 3 ÷ 6 × (600 + 4×336 + 144) = 0.5 × 2,088 = 1,044 m³."
        ],
        "result": "A 30 × 20 m pond, 3 m deep with 2:1 sides, holds 1,044 m³, about 1.04 million litres."
    },
    "interpretation": "Usable storage is less than the full volume: allow for evaporation, seepage and the dead storage below the pump intake. Measure dimensions at the water line you expect, not at the top of the bank.",
    "assumptions": [
        "The pond is rectangular with the same slope on all four sides and a flat floor."
    ],
    "limitations": [
        "Irregular or round ponds need to be approximated or surveyed.",
        "Sediment build-up reduces volume over time."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "Why not just multiply length × width × depth?",
            "answer": "With sloping sides that overstates the volume. For the example it would give 1,800 m³ instead of 1,044 m³."
        },
        {
            "question": "Is the prismoidal formula exact here?",
            "answer": "Yes. For a straight-sided pit whose cross-section changes linearly with depth, the prismoidal formula gives the exact volume."
        }
    ],
    "sources": [],
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            "name": "Rainfall Harvest Volume Calculator",
            "url": "https://calculators.geekmidst.com/calculators/rainfall-harvest-volume-calculator"
        },
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            "name": "Fish Pond Stocking Density Calculator",
            "url": "https://calculators.geekmidst.com/calculators/fish-pond-stocking-density-calculator"
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        {
            "name": "Irrigation Pump Power Calculator",
            "url": "https://calculators.geekmidst.com/calculators/irrigation-pump-power-calculator"
        },
        {
            "name": "Concrete Calculator",
            "url": "https://calculators.geekmidst.com/calculators/concrete-calculator"
        }
    ],
    "disclaimer": null,
    "publisher": "GM¹X CalcVerse"
}