Documentation sections

Voltage Divider Calculator

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

Slug voltage-divider. Calculate voltage divider output voltage, current, Thévenin impedance, and power dissipation from Vin, R1, and R2. Ideal for bias networks and level shifting.

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 voltage-divider
Name	Unit	Range	Default	Description
vinnumber	V	0 … 1000	5	Input Voltage
r1number	Ω	1 … 10000000	10000	R1 (top)
r2number	Ω	1 … 10000000	10000	R2 (bottom)
eSeriesnumber	none	0 … 96	0	Rounds every part to the nearest value in the series; the response and the export are the rounded design's.One of: 0 Ideal values · 12 E12 (10%) · 24 E24 (5%) · 48 E48 (2%) · 96 E96 (1%)

Outputs

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

Outputs of voltage-divider
Field	Unit	Description
voutheadline	V	Output Voltage
ratio	none	Division Ratio
current	A	Quiescent Current
rThev	Ω	Thévenin Impedance
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": "voltage-divider",
    "inputs": {
      "vin": 5,
      "r1": 10000,
      "r2": 10000,
      "eSeries": 0
    }
  }'

import rftools

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

result = client.calculate("voltage-divider", {"vin": 5, "r1": 10000, "r2": 10000, "eSeries": 0})
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": "voltage-divider",
    "inputs": {
      "vin": 5,
      "r1": 10000,
      "r2": 10000,
      "eSeries": 0
    }
  }),
});
console.log(response.status, await response.json());

package main

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

func main() {
	body := []byte(`{
	  "slug": "voltage-divider",
	  "inputs": {
	    "vin": 5,
	    "r1": 10000,
	    "r2": 10000,
	    "eSeries": 0
	  }
	}`)
	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": "voltage-divider",
  "values": {
    "vout": 2.5,
    "current": 0.00025,
    "rThev": 5000,
    "powerR1": 0.000625,
    "powerR2": 0.000625,
    "ratio": 0.5
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:voltage-divider",
    "version": "api@3f2c1a9b04de",
    "formulaRef": null,
    "assumptions": [],
    "validRange": {
      "status": "inside",
      "bounds": {
        "vin": {
          "min": 0,
          "max": 1000,
          "unit": "V"
        },
        "r1": {
          "min": 1,
          "max": 10000000,
          "unit": "Ω"
        },
        "r2": {
          "min": 1,
          "max": 10000000,
          "unit": "Ω"
        },
        "eSeries": {
          "min": 0,
          "max": 96,
          "unit": ""
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "vin": 5,
      "r1": 10000,
      "r2": 10000,
      "eSeries": 0
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

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