xmoo Cable Sizing API

What it does

• Cable sizing from the design current or power: protective device (I_b ≤ I_n ≤ I_z, I₂ ≤ 1.45 I_z), cross-section from the current-carrying capacity with temperature and grouping factors, voltage drop, fault loop and disconnection, short-circuit withstand. If voltage drop or disconnection require it, the cross-section is increased automatically.
• Current-carrying capacity for an installation: tabulated and corrected value for every cross-section, or the smallest one that carries a given current.
• Voltage drop of a cable, the longest length within the limit and the smallest cross-section that keeps it.

Each answer names the standard, table and column it used, and lists the calculation step by step in plain text – ready to show to your users or to put into a report. Nothing is stored. It is the same engine as the free cable sizing tool on this site (in German).

Standards

Current-carrying capacities and correction factors come from DIN VDE 0298-4:2023-06 (Tables 3–6, 17, 20–26, 29). Its values are those of HD 60364-5-52 / IEC 60364-5-52 Annex B, so the API fits every country that uses these tables. The calculation follows IEC 60364-4-43 (overload protection), IEC 60364-5-52 (voltage drop, resistive part) and IEC 60364-4-41 (automatic disconnection) with the minimum single-phase fault current to IEC 60909-0 (c_min = 0.9, conductor at its permissible short-circuit temperature). Supply voltages are 230 V / 400 V.

• Copper and aluminium (aluminium from 25 mm²), PVC 70 °C and cross-linked 90 °C insulation.
• Reference installation methods A1 to G, cross-sections up to 300 mm² (F and G up to 630 mm²).
• Protective devices: circuit breakers type B, C, D up to 63 A, gG fuses up to 250 A; TN and TT systems.

The API is a planning aid without warranty. It replaces neither professional design nor verification to IEC 60364-6. National deviations from these tables are not covered – check the rules that apply where you install.

Access

The API is offered through RapidAPI, where you subscribe to a plan, get your key and the host name for your requests. The listing is being prepared – the link will appear here as soon as it is live. Questions: julian@haag-automation.com.

All endpoints take and return JSON (Content-Type: application/json, body up to 64 KB). The examples expect your key and host in RAPIDAPI_KEY and RAPIDAPI_HOST.

Endpoints

Field descriptions: api.xmoo.app/electrical/openapi.json (OpenAPI 3.0). Descriptive texts are English; lang=de returns German.

Examples

Real answers of the API, shortened where marked. A test on our side sends these requests and checks that the answers still match.

Size a sub-distribution feeder

50 kW three-phase at cos φ 0.95, 30 m, installation method C, 35 °C, gG fuse, distribution circuit, 100 mΩ fault loop impedance up to the origin of the circuit:

curl -s -X POST "https://$RAPIDAPI_HOST/v1/electrical/cable/size" \
  -H "x-rapidapi-key: $RAPIDAPI_KEY" \
  -H "x-rapidapi-host: $RAPIDAPI_HOST" \
  -H "Content-Type: application/json" \
  -d @request.json

{
  "supply": "three-phase",
  "power": 50000,
  "powerFactor": 0.95,
  "length": 30,
  "installationMethod": "C",
  "ambientTemperature": 35,
  "protectiveDevice": "gG",
  "circuitType": "distribution",
  "upstreamImpedance": 100
}

Answer, shortened to the main results and the first of six steps:

{
  "status": "ok",
  "result": {
    "designCurrent": 75.97,
    "protectiveDevice": {
      "type": "gG",
      "ratedCurrent": 80,
      "conventionalCurrentI2": 128
    },
    "requiredCurrentCapacity": 88.28,
    "crossSection": 25,
    "tabulatedCapacity": 96,
    "currentCapacity": 90.24,
    "factors": {
      "temperature": 0.94,
      "grouping": 1
    },
    "voltageDrop": {
      "volts": 2.68,
      "percent": 0.67,
      "ok": true
    },
    "disconnection": {
      "maxTime": 5,
      "disconnectionCurrent": 440,
      "loopImpedance": 0.1669,
      "minShortCircuitCurrent": 1240.58,
      "ok": true
    },
    "shortCircuit": {
      "k": 115,
      "permissibleTime": 5.37,
      "ok": true
    },
    "recommendation": {
      "text": "NYM-J 5×25 mm², 3 × gG 80 A (e.g. NEOZED D03 or NH size 000/00)"
    }
  },
  "sources": {
    "standard": "DIN VDE 0298-4:2023-06",
    "table": "Table 3",
    "hd60364552": "B.52.4/6"
  },
  "steps": [
    {
      "step": 1,
      "title": "Design current Ib",
      "standard": null,
      "status": "ok",
      "lines": [
        "Ib = P ÷ (√3 × U × cos φ) = 50,000 W ÷ (1.732 × 400 V × 0.95) = 75.97 A"
      ],
      "nextStep": null
    }
  ],
  "notice": "Planning aid without warranty; it replaces neither professional design nor verification to IEC 60364-6."
}

status is ok when every check passes, failed when a condition is not met (the step then says what to do in nextStep), incomplete when a step could not be checked – for example without upstreamImpedance – and note when the short-circuit check needs a manufacturer value.

Voltage drop of a final circuit

16 A single-phase, 25 m, 1.5 mm² copper:

{
  "supply": "single-phase",
  "current": 16,
  "length": 25,
  "crossSection": 1.5
}

{
  "designCurrent": 16,
  "voltage": 230,
  "conductivity": 56,
  "voltageDrop": {
    "volts": 9.52,
    "percent": 4.14,
    "ok": false
  },
  "maxLength": 24.15,
  "smallestCrossSectionWithinLimit": {
    "crossSection": 2.5,
    "volts": 5.71,
    "percent": 2.48
  },
  "formula": "ΔU = 2 × L × I × cos φ ÷ (κ × A)",
  "note": "Resistive part only, conductor at 20 °C; the inductive reactance of large cross-sections is not included."
}

4.14 % is above the default limit of 4 %: the cable may be at most 24.15 m long, or 2.5 mm² keeps the drop at 2.48 %.

Which cross-section carries 32 A?

Installation method B2, three loaded conductors, 40 °C ambient:

{
  "installationMethod": "B2",
  "loadedConductors": 3,
  "ambientTemperature": 40,
  "requiredCurrent": 32
}

Answer, shortened to the first three cross-sections of the list:

{
  "conductor": "copper",
  "insulation": "pvc-70",
  "column": {
    "installationMethod": "B2",
    "loadedConductors": 3,
    "arrangement": null
  },
  "factors": {
    "temperature": 0.87,
    "grouping": 1,
    "soil": null,
    "groupingCircuitsInTable": 1,
    "total": 0.87
  },
  "smallestSufficient": {
    "crossSection": 10,
    "tabulatedCapacity": 46,
    "currentCapacity": 40.02
  },
  "capacities": [
    {
      "crossSection": 1.5,
      "tabulatedCapacity": 15,
      "currentCapacity": 13.05
    },
    {
      "crossSection": 2.5,
      "tabulatedCapacity": 20,
      "currentCapacity": 17.4
    },
    {
      "crossSection": 4,
      "tabulatedCapacity": 27,
      "currentCapacity": 23.49
    }
  ],
  "sources": {
    "standard": "DIN VDE 0298-4:2023-06",
    "table": "Table 3",
    "hd60364552": "B.52.4/5",
    "factors": [
      "Table 17",
      "Table 22"
    ]
  }
}

Errors

Errors come as JSON with a code, a message and, for input errors, the field:

{
  "error": {
    "code": "missing_field",
    "message": "\"crossSection\" is required.",
    "field": "crossSection"
  }
}

Use with AI agents (MCP)

RapidAPI offers its APIs as tools for AI agents through the Model Context Protocol (MCP). With your RapidAPI key, an agent can size a cable as a tool call – and show the user the steps behind the result.

Privacy and terms

The inputs are technical values; nothing is stored. API privacy notice · API terms of use · data processing agreement.

Provider

Haag Automation, Julian Haag, Mühlstraße 35, 74360 Ilsfeld, Germany · julian@haag-automation.com · xmoo is a brand of Haag Automation. All APIs