ForHosting KIT · Engineering & construction

NTC thermistor temperature from resistance calculator

A 10 kΩ NTC that measures exactly 10 kΩ is at its 25 °C reference, which is 298.15 K or 77 °F. Enter the measured resistance, the nominal value and beta to read any other temperature in three units. Free in your browser.

Free
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Your data stays on your device

Run — free How it works & API

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Worked example

If you enter

Resistance ohm: 10,000
Nominal resistance ohm: 10,000
Beta kelvin: 3,950
Nominal temperature c: 25

You get

Temperature c: 25
Temperature k: 298.15
Temperature f: 77

This NTC thermistor temperature calculator converts a measured resistance into temperature by inverting the standard beta-model equation. Enter the resistance you measured, the thermistor's nominal resistance, its beta coefficient, and the nominal reference temperature from the datasheet. The result includes degrees Celsius, kelvins, and degrees Fahrenheit. The calculation is deterministic and runs without network access, making it suitable for quick bench checks, firmware verification, sensor calibration workflows, and repeatable automated calculations.

Choose values from the same thermistor specification

Begin with the measured thermistor resistance in ohms. Then enter the nominal resistance stated by the manufacturer, often written as R25 because it applies at 25 degrees Celsius. The beta coefficient must come from the same thermistor datasheet and should cover the temperature interval relevant to your measurement.

Some datasheets publish several beta values, such as one for 25 to 50 degrees Celsius and another for 25 to 85 degrees Celsius. Select the coefficient whose stated interval best matches the operating range. The nominal temperature defaults to 25 degrees Celsius, but you can change it when the resistance reference is specified at another temperature.

All resistance and beta inputs must be positive finite numbers, and the reference temperature must be above absolute zero. Keep resistance units consistent: because the equation uses a resistance ratio, both measured and nominal resistance may be entered in ohms as requested, without converting one value to kilohms while leaving the other in ohms. A mismatched reference value or beta coefficient can produce a plausible-looking result that does not describe the actual component.

How the beta-model inversion works

An NTC thermistor decreases in resistance as its temperature rises. The beta model describes this exponential relationship using the nominal resistance R0, nominal absolute temperature T0, and beta coefficient B. The nominal Celsius temperature is first shifted by 273.15 so every temperature used inside the equation is absolute.

When measured resistance equals nominal resistance, the logarithm is zero, so the calculated temperature equals the nominal temperature; this is a useful input sanity check. For a typical NTC device, resistance above R0 produces a lower temperature than T0, while resistance below R0 produces a higher temperature. The implementation rejects combinations that would imply a nonpositive absolute temperature rather than returning an undefined or misleading numerical value.

Understand accuracy and practical limitations

The beta equation is an approximation, not a complete calibration certificate. Its accuracy depends on thermistor tolerance, beta tolerance, measurement accuracy, lead resistance, self-heating, and how closely the selected beta interval matches the actual temperature. A meter current or voltage-divider current warms the bead slightly, so the resistance can represent a temperature above the surrounding air.

Thermal contact, airflow, encapsulation, and response time also matter when comparing the result with another sensor. For wider ranges or tighter accuracy, use manufacturer Steinhart-Hart coefficients or a calibrated resistance-versus-temperature table when those are available. This calculator is most useful for engineering estimates, diagnostics, software tests, and checking whether a measured resistance is consistent with an expected operating point.

It does not infer the resistance from an ADC voltage or divider circuit; calculate or measure the thermistor resistance first. It also does not account for wiring or parallel leakage automatically. For repeatable work, record the exact part number, coefficient interval, reference resistance, reference temperature, excitation conditions, and meter accuracy alongside the calculated result.

What you can do with it

Check a thermistor on the bench

Convert a multimeter resistance reading into an estimated temperature and compare it with room or chamber conditions.

Verify embedded firmware math

Generate reference temperatures for known resistance values when testing an NTC conversion routine or lookup-table implementation.

Review sensor logs

Transform resistance samples exported by a measurement system when the part's nominal resistance and beta coefficient are known.

FAQ

What is the beta coefficient?

Beta is a thermistor material constant expressed in kelvins. Use the value and temperature interval published for your exact part.

Why is 25 degrees Celsius the default reference temperature?

Many NTC thermistors specify nominal resistance at 25 degrees Celsius, commonly labeled R25. Change the reference when your datasheet uses another temperature.

Can I enter resistance in kilohms?

The fields are defined in ohms. Convert both measured and nominal resistance to ohms before submitting so their scale is consistent and the documented contract is followed.

Why might the calculated temperature differ from the actual temperature?

Thermistor and beta tolerances, meter error, self-heating, thermal contact, lead resistance, and beta-model approximation can all contribute to the difference.

Does this use the Steinhart-Hart equation?

No. It uses the single-coefficient beta model. Steinhart-Hart coefficients or a manufacturer table can provide better accuracy over a broad range.

Related tools

For developers — API access

Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.

API endpoint

POSThttps://api.kit.forhosting.com/elec/ntc-thermistor-temp

Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.

Call it from your stack

curl -X POST https://api.kit.forhosting.com/elec/ntc-thermistor-temp \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"resistance_ohm":10000,"nominal_resistance_ohm":10000,"beta_kelvin":3950}'

const res = await fetch("https://api.kit.forhosting.com/elec/ntc-thermistor-temp", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "resistance_ohm": 10000,
    "nominal_resistance_ohm": 10000,
    "beta_kelvin": 3950
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/elec/ntc-thermistor-temp",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "resistance_ohm": 10000,
    "nominal_resistance_ohm": 10000,
    "beta_kelvin": 3950
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/elec/ntc-thermistor-temp", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"resistance_ohm":10000,"nominal_resistance_ohm":10000,"beta_kelvin":3950}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"resistance_ohm":10000,"nominal_resistance_ohm":10000,"beta_kelvin":3950}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/elec/ntc-thermistor-temp", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "resistance_ohm": 10000,
  "nominal_resistance_ohm": 10000,
  "beta_kelvin": 3950
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "elec.ntc_thermistor_temp",
  "status": "queued",
  "_links": {
    "result": "/tasks/tsk_…/result"
  }
}

The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.

Pricing

Per request$0.002

Published price — no tokens, no invented credits. A failed task is never charged.

Errors

HTTP	Code	Meaning
`401`	`unauthorized`	Missing or invalid API key.
`402`	`insufficient_balance`	Your balance doesn't cover the task price.
`404`	`unknown_type`	That task type doesn't exist.
`429`	`rate_limited`	Too many requests. Use the webhook instead of polling.

Technical notes

How the beta-model inversion works

To recover temperature from a resistance measurement R, the calculator evaluates 1/T = 1/T0 + ln(R/R0)/B, then takes the reciprocal to obtain T in kelvins.

Technical questions

What does the calculation cost?

The calculator runs free in the browser. An API request costs $0.002.

Read the full KIT documentation →

Run — free

Worked example

Choose values from the same thermistor specification

How the beta-model inversion works

Understand accuracy and practical limitations

What you can do with it

Check a thermistor on the bench

Verify embedded firmware math

Review sensor logs

FAQ

Related tools

For developers — API access

API endpoint

Call it from your stack

Example request

Example response

Pricing

Errors

Technical notes

How the beta-model inversion works

Technical questions

thank you