Documentation sections

Minimum Conductor Spacing Calculator

POSThttps://rftools.io/api/py/v1/calculate

Slug minimum-conductor-spacing. Determine minimum electrical clearance between conductors per IPC-2221B Table 6.1 based on voltage and conductor condition.

Inputs

Send every one of these in inputs, in the units shown. Most are required: a call without one is refused (400) and costs nothing; one the calculator can do without takes the default shown. An input outside its range is still computed and flagged in the provenance.

Inputs of minimum-conductor-spacing
Name	Unit	Range	Default	Description
voltagenumber	V	0 … 1000	50	Voltage (DC or Peak AC)
conditionnumber	none	0 … 5	1	The IPC-2221B Table 6-1 column; uncoated external conductors above 3,050 m take column B3One of: 0 B1 Internal · 1 B2 External, uncoated · 2 B4 Polymer coated · 3 A5 Conformal coated · 4 A6 Leads, uncoated · 5 A7 Leads, coated
altitudenumber	m	0 … 30000	0	Operating Altitude
conductorSpacingnumber	mm	0.01 … 50	0.8	The spacing between the two conductors on your board, checked against the IPC-2221B minimum

Outputs

Returned in values, by key. A value that is unbounded or undefined is null.

Outputs of minimum-conductor-spacing
Field	Unit	Description
spacingheadline	mm	Minimum Spacing
spacingMils	mil	Minimum Spacing
altitudeFactor	×	The applied spacing over its sea-level value: B3/B2 for an uncoated board above 3,050 m, 1 otherwise
spacingB1	mm	B1 (Internal)
spacingB2	mm	B2 (External Uncoated, to 3,050 m)
spacingB3	mm	B3 (External Uncoated, above 3,050 m)
spacingB4	mm	Column B4: external conductors with a permanent polymer coating (solder resist)
spacingPercent	%	The minimum spacing as a percentage of the spacing on the board; above 100 % the board does not comply
maxVoltage	V	The highest voltage at which the spacing on the board meets the IPC-2221B minimum for this condition

Calling it

Calculate: one call, the request and response in full, and its errors.
Batch: this calculator with others, or a sweep, in one request.
Solve for a target: the value of one input that brings an output to a target.

curl -X POST https://rftools.io/api/py/v1/calculate \
  -H "X-API-Key: $RFTOOLS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "slug": "minimum-conductor-spacing",
    "inputs": {
      "voltage": 50,
      "condition": 1,
      "altitude": 0,
      "conductorSpacing": 0.8
    }
  }'

import rftools

client = rftools.Client()  # reads RFTOOLS_API_KEY, or the key `rftools login` saved

result = client.calculate("minimum-conductor-spacing", {"voltage": 50, "condition": 1, "altitude": 0, "conductorSpacing": 0.8})
print(result.values)
print(result.warnings, result.provenance.formula_ref)

const response = await fetch("https://rftools.io/api/py/v1/calculate", {
  method: "POST",
  headers: {
    "X-API-Key": process.env.RFTOOLS_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "slug": "minimum-conductor-spacing",
    "inputs": {
      "voltage": 50,
      "condition": 1,
      "altitude": 0,
      "conductorSpacing": 0.8
    }
  }),
});
console.log(response.status, await response.json());

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	body := []byte(`{
	  "slug": "minimum-conductor-spacing",
	  "inputs": {
	    "voltage": 50,
	    "condition": 1,
	    "altitude": 0,
	    "conductorSpacing": 0.8
	  }
	}`)
	req, err := http.NewRequest("POST", "https://rftools.io/api/py/v1/calculate", bytes.NewReader(body))
	if err != nil {
		panic(err)
	}
	req.Header.Set("X-API-Key", os.Getenv("RFTOOLS_API_KEY"))
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(res.Status, string(out))
}

application/json

{
  "slug": "minimum-conductor-spacing",
  "values": {
    "spacing": 0.6,
    "spacingMils": 23.62204724409449,
    "altitudeFactor": 1,
    "spacingB1": 0.1,
    "spacingB2": 0.6,
    "spacingB3": 0.6,
    "spacingB4": 0.13,
    "spacingPercent": 74.99999999999999,
    "maxVoltage": 150
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:minimum-conductor-spacing",
    "version": "api@3f2c1a9b04de",
    "formulaRef": "IPC-2221B (2012) Table 6-1 and §6.3, as given by pcbsync, Altium and trafolo (agreeing cell for cell)",
    "assumptions": [],
    "validRange": {
      "status": "inside",
      "bounds": {
        "voltage": {
          "min": 0,
          "max": 1000,
          "unit": "V"
        },
        "condition": {
          "min": 0,
          "max": 5,
          "unit": ""
        },
        "altitude": {
          "min": 0,
          "max": 30000,
          "unit": "m"
        },
        "conductorSpacing": {
          "min": 0.01,
          "max": 50,
          "unit": "mm"
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "voltage": 50,
      "condition": 1,
      "altitude": 0,
      "conductorSpacing": 0.8
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "voltage"
      ],
      "msg": "Input should be a valid number, unable to parse string as a number",
      "input": "abc"
    }
  ]
}

An input sent as text. Nothing was counted.

{
  "detail": "More than 120 requests in 60 seconds from this address.",
  "errorKind": "rate_limited",
  "limit": 120,
  "windowSeconds": 60,
  "upgradeUrl": "https://rftools.io/pricing/"
}

Too many requests in a minute, with Retry-After.

Same inputs on the calculator pageMinimum Conductor Spacing Calculator, at these values