{
    "name": "Hydrostatic Pressure Calculator",
    "url": "https://calculators.geekmidst.com/calculators/hydrostatic-pressure-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/hydrostatic-pressure-calculator.md",
    "category": "Science & engineering",
    "description": "Work out gauge and absolute pressure at a depth in water or any liquid, or the depth that gives a chosen pressure, from density, depth and g.",
    "summary": "Pressure in a still liquid rises with depth by ρ g h, regardless of the container’s shape. Add the pressure at the surface to get the absolute pressure.",
    "also_called": [
        "Pressure at depth calculator",
        "Water head pressure 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": "solve",
            "label": "Solve for",
            "type": "segmented",
            "default": "pressure",
            "options": {
                "pressure": "Pressure",
                "depth": "Depth"
            }
        },
        {
            "name": "density",
            "label": "Liquid density",
            "type": "number",
            "default": "1000"
        },
        {
            "name": "density_unit",
            "label": "Density unit",
            "type": "select",
            "default": "kgm3",
            "options": {
                "kgm3": "kg/m³",
                "gcm3": "g/cm³",
                "lbft3": "lb/ft³"
            }
        },
        {
            "name": "depth",
            "label": "Depth below the surface",
            "type": "number",
            "default": "10",
            "shown_when": {
                "solve": "pressure"
            }
        },
        {
            "name": "depth_unit",
            "label": "Depth unit",
            "type": "select",
            "default": "m",
            "options": {
                "m": "metres (m)",
                "cm": "centimetres (cm)",
                "mm": "millimetres (mm)",
                "km": "kilometres (km)",
                "ft": "feet (ft)",
                "in": "inches (in)",
                "mi": "miles (mi)"
            }
        },
        {
            "name": "pressure",
            "label": "Gauge pressure",
            "type": "number",
            "default": "100",
            "shown_when": {
                "solve": "depth"
            }
        },
        {
            "name": "pressure_unit",
            "label": "Pressure unit",
            "type": "select",
            "default": "kpa",
            "options": {
                "pa": "pascals (Pa)",
                "kpa": "kilopascals (kPa)",
                "mpa": "megapascals (MPa)",
                "bar": "bar",
                "atm": "atmospheres (atm)",
                "psi": "psi",
                "mmhg": "mmHg"
            }
        },
        {
            "name": "surface_pressure",
            "label": "Pressure at the surface",
            "type": "number",
            "default": "101.325",
            "unit": "kPa"
        },
        {
            "name": "gravity",
            "label": "Gravitational acceleration (g)",
            "type": "number",
            "default": "9.80665",
            "unit": "m/s²"
        }
    ],
    "outputs": [
        {
            "key": "answer",
            "label": "Result",
            "format": "text"
        },
        {
            "key": "gauge_kpa",
            "label": "Gauge pressure",
            "format": "number"
        },
        {
            "key": "absolute_kpa",
            "label": "Absolute pressure",
            "format": "number"
        },
        {
            "key": "gauge_bar",
            "label": "Gauge pressure",
            "format": "number"
        },
        {
            "key": "gauge_psi",
            "label": "Gauge pressure",
            "format": "number"
        },
        {
            "key": "absolute_atm",
            "label": "Absolute pressure",
            "format": "number"
        },
        {
            "key": "depth_m",
            "label": "Depth",
            "format": "number"
        },
        {
            "key": "depth_ft",
            "label": "Depth",
            "format": "number"
        }
    ],
    "formula": {
        "text": "P_gauge = ρ g h;  P_abs = P_surface + ρ g h;  h = P_gauge ÷ (ρ g)",
        "variables": {
            "ρ": "liquid density in kg/m³",
            "g": "gravitational acceleration",
            "h": "vertical depth below the free surface in m",
            "P_surface": "pressure acting on the surface (atmospheric if open to air)"
        }
    },
    "worked_example": {
        "inputs": {
            "solve": "pressure",
            "density": "1000",
            "density_unit": "kgm3",
            "depth": "10",
            "depth_unit": "m",
            "pressure": "100",
            "pressure_unit": "kpa",
            "surface_pressure": "101.325",
            "gravity": "9.80665"
        },
        "steps": [
            "P_gauge = 1,000 × 9.80665 × 10 = 98,066.5 Pa = 98.0665 kPa.",
            "P_abs = 101.325 + 98.0665 = 199.39 kPa, about 1.97 atm."
        ],
        "result": "Ten metres down in fresh water the pressure is about 98 kPa above atmospheric, so roughly double the surface pressure in absolute terms."
    },
    "interpretation": "Divers use the rule of thumb that every 10 m of seawater adds about one atmosphere. Tank walls and dams must resist pressure that grows linearly with depth, so the bottom carries the most load.",
    "assumptions": [
        "Liquid at rest with constant density (incompressible)."
    ],
    "limitations": [
        "Density changes with temperature and salinity; very deep ocean water is slightly compressed.",
        "Not for moving fluids; see the Bernoulli Equation Calculator."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "Does the shape of the container matter?",
            "answer": "No. Pressure depends only on the vertical depth, not on the volume or shape above (the hydrostatic paradox)."
        },
        {
            "question": "What is the difference between gauge and absolute pressure?",
            "answer": "Gauge pressure is measured relative to the atmosphere; absolute pressure includes it. Tyre gauges read gauge pressure."
        }
    ],
    "sources": [
        {
            "title": "BIPM: The International System of Units (SI)",
            "url": "https://www.bipm.org/"
        }
    ],
    "related": [
        {
            "name": "Pressure Calculator",
            "url": "https://calculators.geekmidst.com/calculators/pressure-calculator"
        },
        {
            "name": "Buoyancy Calculator",
            "url": "https://calculators.geekmidst.com/calculators/buoyancy-calculator"
        },
        {
            "name": "Bernoulli Equation Calculator",
            "url": "https://calculators.geekmidst.com/calculators/bernoulli-equation-calculator"
        },
        {
            "name": "Density Calculator",
            "url": "https://calculators.geekmidst.com/calculators/density-calculator"
        }
    ],
    "disclaimer": null,
    "publisher": "GM¹X CalcVerse"
}