{
  "slug": "resistor-parallel",
  "title": "Parallel & Series Resistor Calculator",
  "heading": "Resistor Combination Calculator",
  "category": "math",
  "url": "https://www.revenuelab.fyi/toolbox/resistor-parallel",
  "summary": "Equivalent resistance for up to four resistors.",
  "description": "Series adds; parallel takes the reciprocal sum. Leave a resistor at zero to skip it.",
  "formula": "Series: R = ΣR. Parallel: 1/R = Σ(1/Rᵢ)",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=resistor-parallel",
  "inputs": [
    {
      "id": "r1",
      "label": "R1",
      "kind": "number",
      "hint": null,
      "default": 100,
      "unit": "Ω",
      "min": 0,
      "max": null
    },
    {
      "id": "r2",
      "label": "R2",
      "kind": "number",
      "hint": null,
      "default": 220,
      "unit": "Ω",
      "min": 0,
      "max": null
    },
    {
      "id": "r3",
      "label": "R3 (0 to skip)",
      "kind": "number",
      "hint": null,
      "default": 0,
      "unit": "Ω",
      "min": 0,
      "max": null
    },
    {
      "id": "r4",
      "label": "R4 (0 to skip)",
      "kind": "number",
      "hint": null,
      "default": 0,
      "unit": "Ω",
      "min": 0,
      "max": null
    }
  ],
  "outputs": [
    {
      "id": "parallel",
      "label": "Parallel equivalent (Ω)",
      "format": "decimal",
      "hint": null,
      "primary": true
    },
    {
      "id": "series",
      "label": "Series equivalent (Ω)",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "count",
      "label": "Resistors used",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "ratio",
      "label": "Parallel ÷ series",
      "format": "decimal",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "R1: 100 Ω",
      "R2: 220 Ω",
      "R3 (0 to skip): 0 Ω",
      "R4 (0 to skip): 0 Ω"
    ],
    "outputs": [
      "Parallel equivalent (Ω): 68.75",
      "Series equivalent (Ω): 320",
      "Resistors used: 2",
      "Parallel ÷ series: 0.2148"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter r1 (Ω).",
      "Enter r2 (Ω).",
      "Enter r3 (0 to skip) (Ω).",
      "Enter r4 (0 to skip) (Ω).",
      "Read your parallel equivalent (ω) on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "r1": 60,
        "r2": 132,
        "r3": 0,
        "r4": 0
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "r1": 100,
        "r2": 220,
        "r3": 0,
        "r4": 0
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "r1": 160,
        "r2": 352,
        "r3": 0,
        "r4": 0
      }
    }
  ],
  "limitations": [
    "Results are rounded for display; the underlying calculation keeps full precision.",
    "Very large or very small inputs may hit floating-point limits in the browser.",
    "Inputs outside the accepted range are clamped rather than rejected."
  ],
  "faq": [
    {
      "q": "How does the resistor combination calculator work?",
      "a": "Series adds; parallel takes the reciprocal sum. Leave a resistor at zero to skip it. The underlying maths is: Series: R = ΣR. Parallel: 1/R = Σ(1/Rᵢ)"
    },
    {
      "q": "What do I need to enter?",
      "a": "4 values: r1, r2, r3 (0 to skip), and r4 (0 to skip). Each field starts with a sensible default, so you can change one number at a time and watch the result move."
    },
    {
      "q": "What does the parallel equivalent (ω) result mean?",
      "a": "It is returned as a decimal number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds."
    },
    {
      "q": "Is this calculator free, and do I need an account?",
      "a": "Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser."
    },
    {
      "q": "How accurate is the result?",
      "a": "It applies the standard formula exactly, so the arithmetic is precise. Results are rounded for display; the underlying calculation keeps full precision."
    },
    {
      "q": "Who is this tool for?",
      "a": "It's built for students, developers, and anyone who needs the answer right now without setting up a spreadsheet."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/ohms-law"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Parallel & Series Resistor Calculator (https://www.revenuelab.fyi/toolbox/resistor-parallel)"
}