{
  "id": "heat-sink",
  "slug": "heat-sink-calculator",
  "url": "https://electronics.tools/tools/heat-sink-calculator/",
  "name": "Heat Sink Temperature Calculator",
  "group": "power-thermal",
  "summary": "Tj = Ta + P Σθ. 10 W at 25 °C with 1.5+0.5+3 °C/W is 75 °C.",
  "formulas": [
    {
      "id": "tj",
      "label": "Junction temperature",
      "plain": "Tj = Ta + P (θJC + θCS + θSA)",
      "mathml": "<math display=\"block\" xmlns=\"http://www.w3.org/1998/Math/MathML\" aria-label=\"Tj = Ta + P (θJC + θCS + θSA)\"><mrow><msub><mi>T</mi><mi>j</mi></msub><mo>=</mo><msub><mi>T</mi><mi>a</mi></msub><mo>+</mo><mi>P</mi><mrow><mo>(</mo><mrow><msub><mi>θ</mi><mi>JC</mi></msub><mo>+</mo><msub><mi>θ</mi><mi>CS</mi></msub><mo>+</mo><msub><mi>θ</mi><mi>SA</mi></msub></mrow><mo>)</mo></mrow></mrow></math>",
      "symbols": [
        "Tj",
        "Ta",
        "P",
        "θJC",
        "θCS",
        "θSA"
      ],
      "sources": [
        "jesd51"
      ]
    },
    {
      "id": "pmax",
      "label": "Power budget",
      "plain": "Pmax = (Tjmax − Ta) / Σθ",
      "mathml": "<math display=\"block\" xmlns=\"http://www.w3.org/1998/Math/MathML\" aria-label=\"Pmax = (Tjmax − Ta) / Σθ\"><mrow><msub><mi>P</mi><mtext>max</mtext></msub><mo>=</mo><mfrac><mrow><msub><mi>T</mi><mrow><mi>j</mi><mo>,</mo><mtext>max</mtext></mrow></msub><mo>-</mo><msub><mi>T</mi><mi>a</mi></msub></mrow><mrow><mo>Σ</mo><mi>θ</mi></mrow></mfrac></mrow></math>",
      "symbols": [
        "Pmax",
        "Tjmax",
        "Ta"
      ],
      "sources": [
        "jesd51"
      ]
    },
    {
      "id": "rsa",
      "label": "Required heat-sink",
      "plain": "θSA_req = (Tjmax − Ta)/P − θJC − θCS",
      "mathml": "<math display=\"block\" xmlns=\"http://www.w3.org/1998/Math/MathML\" aria-label=\"θSA_req = (Tjmax − Ta)/P − θJC − θCS\"><mrow><msub><mi>θ</mi><mtext>SA_req</mtext></msub><mo>=</mo><mfrac><mrow><msub><mi>T</mi><mrow><mi>j</mi><mo>,</mo><mtext>max</mtext></mrow></msub><mo>-</mo><msub><mi>T</mi><mi>a</mi></msub></mrow><mi>P</mi></mfrac><mo>-</mo><msub><mi>θ</mi><mi>JC</mi></msub><mo>-</mo><msub><mi>θ</mi><mi>CS</mi></msub></mrow></math>",
      "symbols": [
        "θSA_req",
        "Tjmax",
        "Ta",
        "P",
        "θJC",
        "θCS"
      ],
      "sources": [
        "jesd51"
      ]
    }
  ],
  "variables": [
    {
      "symbol": "mode",
      "name": "Mode",
      "unit": "1",
      "role": "input",
      "precision": {
        "sig": 1
      },
      "default": "forward",
      "urlParam": "mode"
    },
    {
      "symbol": "P",
      "name": "Dissipation",
      "unit": "W",
      "role": "input",
      "precision": {
        "sig": 4
      },
      "range": {
        "min": 0
      },
      "default": 10,
      "urlParam": "p"
    },
    {
      "symbol": "Ta",
      "name": "Ambient",
      "unit": "°C",
      "role": "input",
      "precision": {
        "sig": 4
      },
      "default": 25,
      "urlParam": "ta"
    },
    {
      "symbol": "θJC",
      "name": "Junction-to-case",
      "unit": "°C/W",
      "role": "input",
      "precision": {
        "sig": 4
      },
      "range": {
        "min": 0
      },
      "default": 1.5,
      "urlParam": "thjc"
    },
    {
      "symbol": "θCS",
      "name": "Case-to-sink",
      "unit": "°C/W",
      "role": "input",
      "precision": {
        "sig": 4
      },
      "range": {
        "min": 0
      },
      "default": 0.5,
      "urlParam": "thcs"
    },
    {
      "symbol": "θSA",
      "name": "Sink-to-ambient",
      "unit": "°C/W",
      "role": "input",
      "precision": {
        "sig": 4
      },
      "range": {
        "min": 0
      },
      "default": 3,
      "urlParam": "thsa"
    },
    {
      "symbol": "Tjmax",
      "name": "Tj max (blank → 150 °C)",
      "unit": "°C",
      "role": "input",
      "precision": {
        "sig": 4
      },
      "default": 150,
      "urlParam": "tjmax"
    },
    {
      "symbol": "Tj",
      "name": "Junction temperature",
      "unit": "°C",
      "role": "output",
      "precision": {
        "sig": 4
      }
    },
    {
      "symbol": "Pmax",
      "name": "Power budget",
      "unit": "W",
      "role": "output",
      "precision": {
        "sig": 4
      }
    },
    {
      "symbol": "sum",
      "name": "Σθ",
      "unit": "°C/W",
      "role": "output",
      "precision": {
        "sig": 4
      }
    },
    {
      "symbol": "m",
      "name": "Tjmax − Tj",
      "unit": "°C",
      "role": "output",
      "precision": {
        "sig": 4
      }
    },
    {
      "symbol": "over",
      "name": "Tj > Tjmax",
      "unit": "1",
      "role": "output",
      "precision": {
        "sig": 1
      }
    },
    {
      "symbol": "θSA_req",
      "name": "Required θSA",
      "unit": "°C/W",
      "role": "output",
      "precision": {
        "sig": 4
      }
    }
  ],
  "examples": [
    {
      "id": "10w-25c",
      "title": "10 W, 25 °C, 1.5 / 0.5 / 3 °C/W",
      "input": [
        {
          "symbol": "mode",
          "value": "forward",
          "unit": "1",
          "display": "forward"
        },
        {
          "symbol": "P",
          "value": 10,
          "unit": "W",
          "display": "10 W"
        },
        {
          "symbol": "Ta",
          "value": 25,
          "unit": "°C",
          "display": "25 °C"
        },
        {
          "symbol": "θJC",
          "value": 1.5,
          "unit": "°C/W",
          "display": "1.5 °C/W"
        },
        {
          "symbol": "θCS",
          "value": 0.5,
          "unit": "°C/W",
          "display": "0.5 °C/W"
        },
        {
          "symbol": "θSA",
          "value": 3,
          "unit": "°C/W",
          "display": "3 °C/W"
        },
        {
          "symbol": "Tjmax",
          "value": 150,
          "unit": "°C",
          "display": "150 °C"
        }
      ],
      "output": [
        {
          "symbol": "Tj",
          "value": 75,
          "unit": "°C",
          "display": "75 °C"
        },
        {
          "symbol": "Pmax",
          "value": 25,
          "unit": "W",
          "display": "25 W"
        },
        {
          "symbol": "sum",
          "value": 5,
          "unit": "°C/W",
          "display": "5 °C/W"
        },
        {
          "symbol": "over",
          "value": "no",
          "unit": "1",
          "display": "no"
        }
      ],
      "computedBy": "heatSink"
    },
    {
      "id": "solve-rsa",
      "title": "Required θSA for Tjmax 125 °C",
      "input": [
        {
          "symbol": "mode",
          "value": "solve_theta_SA",
          "unit": "1",
          "display": "solve_theta_SA"
        },
        {
          "symbol": "P",
          "value": 10,
          "unit": "W",
          "display": "10 W"
        },
        {
          "symbol": "Ta",
          "value": 25,
          "unit": "°C",
          "display": "25 °C"
        },
        {
          "symbol": "θJC",
          "value": 1.5,
          "unit": "°C/W",
          "display": "1.5 °C/W"
        },
        {
          "symbol": "θCS",
          "value": 0.5,
          "unit": "°C/W",
          "display": "0.5 °C/W"
        },
        {
          "symbol": "Tjmax",
          "value": 125,
          "unit": "°C",
          "display": "125 °C"
        }
      ],
      "output": [
        {
          "symbol": "θSA_req",
          "value": 8,
          "unit": "°C/W",
          "display": "8 °C/W"
        }
      ],
      "computedBy": "heatSink"
    }
  ],
  "sources": [
    {
      "title": "JEDEC JESD51 — Methodology for the Thermal Measurement of Component Packages (Single Semiconductor Device)",
      "url": "https://www.jedec.org/standards-documents/docs/jesd-51",
      "retrieved": "2026-11-02",
      "standard": "JESD51"
    }
  ],
  "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/battery-life-calculator/",
    "https://electronics.tools/tools/power-calculator/"
  ]
}