{
  "id": "capacitor-discharge",
  "slug": "capacitor-discharge-calculator",
  "url": "https://electronics.tools/tools/capacitor-discharge-calculator/",
  "name": "Capacitor Discharge Calculator",
  "group": "cap-ind",
  "summary": "t = RC ln(V0/Vs). 1000 µF, 400 V → 60 V through 10 kΩ is 18.97 s.",
  "formulas": [
    {
      "id": "time",
      "label": "Discharge time",
      "plain": "t = RC ln(V0 / Vs)",
      "mathml": "<math display=\"block\" xmlns=\"http://www.w3.org/1998/Math/MathML\" aria-label=\"t = RC ln(V0 / Vs)\"><mrow><mi>t</mi><mo>=</mo><mi>R</mi><mi>C</mi><mi>ln</mi><mrow><mo>(</mo><mrow><msub><mi>V</mi><mn>0</mn></msub><mo>/</mo><msub><mi>V</mi><mi>s</mi></msub></mrow><mo>)</mo></mrow></mrow></math>",
      "symbols": [
        "t",
        "R",
        "C",
        "V0",
        "Vs"
      ],
      "sources": [
        "iec62368"
      ]
    },
    {
      "id": "resistor",
      "label": "Resistor from time",
      "plain": "R = t / (C ln(V0 / Vs))",
      "mathml": "<math display=\"block\" xmlns=\"http://www.w3.org/1998/Math/MathML\" aria-label=\"R = t / (C ln(V0 / Vs))\"><mrow><mi>R</mi><mo>=</mo><mfrac><mi>t</mi><mrow><mi>C</mi><mi>ln</mi><mrow><mo>(</mo><mrow><msub><mi>V</mi><mn>0</mn></msub><mo>/</mo><msub><mi>V</mi><mi>s</mi></msub></mrow><mo>)</mo></mrow></mrow></mfrac></mrow></math>",
      "symbols": [
        "R",
        "t",
        "C",
        "V0",
        "Vs"
      ],
      "sources": [
        "iec62368"
      ]
    }
  ],
  "variables": [
    {
      "symbol": "mode",
      "name": "Solve",
      "unit": "1",
      "role": "input",
      "precision": {
        "sig": 1
      },
      "default": "time-from-r",
      "urlParam": "mode"
    },
    {
      "symbol": "C",
      "name": "Capacitance",
      "unit": "F",
      "role": "input",
      "precision": {
        "sig": 4
      },
      "range": {
        "min": 0
      },
      "default": 0.001,
      "urlParam": "c"
    },
    {
      "symbol": "V0",
      "name": "Initial voltage",
      "unit": "V",
      "role": "input",
      "precision": {
        "sig": 4
      },
      "range": {
        "min": 0
      },
      "default": 400,
      "urlParam": "v0"
    },
    {
      "symbol": "Vs",
      "name": "Safe voltage (default 60 V, IEC 62368-1 ES1 DC reference)",
      "unit": "V",
      "role": "input",
      "precision": {
        "sig": 4
      },
      "range": {
        "min": 0,
        "note": "IEC 62368-1 ES1 DC reference — not a hard legal limit"
      },
      "default": 60,
      "urlParam": "vs"
    },
    {
      "symbol": "R",
      "name": "Discharge resistor",
      "unit": "Ω",
      "role": "input",
      "precision": {
        "sig": 4
      },
      "range": {
        "min": 0
      },
      "default": 10000,
      "urlParam": "r"
    },
    {
      "symbol": "t",
      "name": "Discharge time",
      "unit": "s",
      "role": "output",
      "precision": {
        "sig": 4
      }
    },
    {
      "symbol": "I0",
      "name": "Initial current",
      "unit": "A",
      "role": "output",
      "precision": {
        "sig": 4
      }
    },
    {
      "symbol": "P0",
      "name": "Initial pulse power",
      "unit": "W",
      "role": "output",
      "precision": {
        "sig": 4
      }
    },
    {
      "symbol": "E",
      "name": "Stored energy",
      "unit": "J",
      "role": "output",
      "precision": {
        "sig": 4
      }
    }
  ],
  "examples": [
    {
      "id": "1mf-400v-10k",
      "title": "1000 µF, 400 V → 60 V ES1 reference, 10 kΩ",
      "input": [
        {
          "symbol": "mode",
          "value": "time-from-r",
          "unit": "1",
          "display": "time-from-r"
        },
        {
          "symbol": "C",
          "value": 0.001,
          "unit": "F",
          "display": "1 mF"
        },
        {
          "symbol": "V0",
          "value": 400,
          "unit": "V",
          "display": "400 V"
        },
        {
          "symbol": "Vs",
          "value": 60,
          "unit": "V",
          "display": "60 V"
        },
        {
          "symbol": "R",
          "value": 10000,
          "unit": "Ω",
          "display": "10 kΩ"
        }
      ],
      "output": [
        {
          "symbol": "t",
          "value": 18.971199848858813,
          "unit": "s",
          "display": "18.97 s"
        },
        {
          "symbol": "P0",
          "value": 16,
          "unit": "W",
          "display": "16 W"
        },
        {
          "symbol": "I0",
          "value": 0.04,
          "unit": "A",
          "display": "40 mA"
        },
        {
          "symbol": "E",
          "value": 80,
          "unit": "J",
          "display": "80 J"
        }
      ],
      "computedBy": "capacitorDischarge"
    },
    {
      "id": "1mf-400v-50v",
      "title": "1000 µF, 400 V → 50 V, 10 kΩ",
      "input": [
        {
          "symbol": "mode",
          "value": "time-from-r",
          "unit": "1",
          "display": "time-from-r"
        },
        {
          "symbol": "C",
          "value": 0.001,
          "unit": "F",
          "display": "1 mF"
        },
        {
          "symbol": "V0",
          "value": 400,
          "unit": "V",
          "display": "400 V"
        },
        {
          "symbol": "Vs",
          "value": 50,
          "unit": "V",
          "display": "50 V"
        },
        {
          "symbol": "R",
          "value": 10000,
          "unit": "Ω",
          "display": "10 kΩ"
        }
      ],
      "output": [
        {
          "symbol": "t",
          "value": 20.79441541679836,
          "unit": "s",
          "display": "20.79 s"
        },
        {
          "symbol": "P0",
          "value": 16,
          "unit": "W",
          "display": "16 W"
        },
        {
          "symbol": "I0",
          "value": 0.04,
          "unit": "A",
          "display": "40 mA"
        },
        {
          "symbol": "E",
          "value": 80,
          "unit": "J",
          "display": "80 J"
        }
      ],
      "computedBy": "capacitorDischarge"
    },
    {
      "id": "470uf-10s",
      "title": "470 µF, 350 V → 36 V in 10 s",
      "input": [
        {
          "symbol": "mode",
          "value": "r-from-time",
          "unit": "1",
          "display": "r-from-time"
        },
        {
          "symbol": "C",
          "value": 0.00047,
          "unit": "F",
          "display": "470 µF"
        },
        {
          "symbol": "V0",
          "value": 350,
          "unit": "V",
          "display": "350 V"
        },
        {
          "symbol": "Vs",
          "value": 36,
          "unit": "V",
          "display": "36 V"
        }
      ],
      "output": [
        {
          "symbol": "R",
          "value": 9354.758510894308,
          "unit": "Ω",
          "display": "9.355 kΩ"
        },
        {
          "symbol": "P0",
          "value": 13.094939848777464,
          "unit": "W",
          "display": "13.09 W"
        },
        {
          "symbol": "E",
          "value": 28.7875,
          "unit": "J",
          "display": "28.79 J"
        }
      ],
      "computedBy": "capacitorDischarge"
    }
  ],
  "sources": [
    {
      "title": "IEC 62368-1 Audio/video, information and communication technology equipment — ES1 DC voltage (reference only)",
      "url": "https://webstore.iec.ch/publication/27412",
      "retrieved": "2026-11-02",
      "standard": "IEC 62368-1"
    }
  ],
  "datePublished": "2026-11-02T00:00:00+08:00",
  "dateModified": "2026-11-02T00:00:00+08:00",
  "author": {
    "name": "Jasper",
    "url": "https://electronics.tools/about/#jasper"
  },
  "relatedTools": [
    "https://electronics.tools/tools/rc-time-constant-calculator/",
    "https://electronics.tools/tools/capacitor-energy-calculator/"
  ]
}