Documentation sections

Current Divider Calculator

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

Slug current-divider. Calculate current division between two parallel resistors using the current divider rule. Computes branch currents I1 and I2, parallel resistance, voltage, and power dissipation in each resistor.

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 current-divider
Name	Unit	Range	Default	Description
totalCurrentnumber	A	0 … 1000	1	Total Current
r1number	Ω	0.001 … 1000000000	1000	R1
r2number	Ω	0.001 … 1000000000	2000	R2

Outputs

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

Outputs of current-divider
Field	Unit	Description
i1headline	A	Current through R1
i2	A	Current through R2
voltage	V	Voltage across parallel combination
rParallel	Ω	Parallel Resistance
powerR1	W	Power in R1
powerR2	W	Power in R2

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": "current-divider",
    "inputs": {
      "totalCurrent": 1,
      "r1": 1000,
      "r2": 2000
    }
  }'

import rftools

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

result = client.calculate("current-divider", {"totalCurrent": 1, "r1": 1000, "r2": 2000})
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": "current-divider",
    "inputs": {
      "totalCurrent": 1,
      "r1": 1000,
      "r2": 2000
    }
  }),
});
console.log(response.status, await response.json());

package main

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

func main() {
	body := []byte(`{
	  "slug": "current-divider",
	  "inputs": {
	    "totalCurrent": 1,
	    "r1": 1000,
	    "r2": 2000
	  }
	}`)
	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": "current-divider",
  "values": {
    "i1": 0.6666666666666666,
    "i2": 0.3333333333333333,
    "rParallel": 666.6666666666666,
    "voltage": 666.6666666666666,
    "powerR1": 444.4444444444444,
    "powerR2": 222.2222222222222
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:current-divider",
    "version": "api@3f2c1a9b04de",
    "formulaRef": "Hayt & Kemmerly, Engineering Circuit Analysis, 8th ed.",
    "assumptions": [],
    "validRange": {
      "status": "inside",
      "bounds": {
        "totalCurrent": {
          "min": 0,
          "max": 1000,
          "unit": "A"
        },
        "r1": {
          "min": 0.001,
          "max": 1000000000,
          "unit": "Ω"
        },
        "r2": {
          "min": 0.001,
          "max": 1000000000,
          "unit": "Ω"
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "totalCurrent": 1,
      "r1": 1000,
      "r2": 2000
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "totalCurrent"
      ],
      "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 pageCurrent Divider Calculator, at these values