RTD Resistance To Temperature Calculator

Are you looking for a fast way to calculate RTD resistance to temperature? This online RTD conversion calculator determines the optimal temperature for Pt100, Pt500, and Pt1000 ohms (Ω) platinum resistance thermometers. 

Some people can’t rely solely on calculators to determine precise temperature. Now, do you want to learn how to calculate the temperature from resistance by yourself? As a bonus, we’ll tell you the fundamental RTD temperature calculation formulas. 

Online Resistance vs Temperature Calculator


RTD resistance (ohms):

This temperature & RTD coefficient calculator supports different types of platinum resistance thermometers (Pt10-Pt1000 ohms to degrees). 

To use our calculator:

  1. Enter the RTD resistance value (the initial resistance value of 100 ohms set to 0°C)
  2. Enter the temperature value in °C
  3. Get the temperature coefficient value (°C) and resistance RTD value (ohms - Ω)

Sound complicated? Let’s break down the basics.

Why Convert Resistance to Temperature?

How RTD resistance changes with temperature

The Resistive Temperature Detector (RTD) is a sensor used for accurate temperature measurement. This device is capable of determining precise temperature values with less than 0.1°C (32.18°F) margin of error.

Many industrial, medical, and commercial processes require specific temperature ranges. That’s understandable, given that the temperature affects energy consumption, chemical; reactions, plants, and health conditions. 

You can measure temperatures with different devices, like thermistors and thermocouples. However, RTDs offer the most accurate measurements in any given environment. You can use the reading with RTD (ohms) to degrees calculator to determine the optimal temperature.

The accuracy depends on the combination of base resistance tolerance and temperature resistance tolerance coefficient. The platinum resistance thermometers (Pt) used in RTDs use platinum elements that increase resistance with temperature. In other words, the resistance of the Pt increases along with the sensor’s temperature.

The RTD temperature calculation is usually made at 0°C with 100 ohms resistance. The most common types of platinum resistance thermometers are:

  • Pt100 (100 ohms resistance at 0°C)
  • Pt500 (500 ohms at 0°C)
  • Pt1000 (1000 ohms at 0°C)

So, how do you calculate RTD resistance to temperature? Let’s find out.

How to Calculate The Resistance to Temperature?

Formula showing how to calculate the temperature coefficient of resistance

You can relate resistance to temperature with the following RTD calculation formula:

Rt = Rref × [1 + α × (T − Tref)]

In this equation, Rt refers to the RTD Resistance at a given temperature (in ohms), Rref means RTD Resistance at the referenced temperature (in ohms), and α is the temperature-resistance coefficient (in ohms per ohm/degree). The ohms are often shown as in the equation.

The T and Tref stand for temperature and reference temperature. Now, how to calculate the temperature from RTD resistance using this formula? Here’s an example.

RTD temperature calculation formula

Let’s assume you have a Pt100 RTD sensor. With a 35°C temperature, 0.00392 temp coefficient value, 0°C reference temp. Your RTD calculation formula will go like this:

RT = 100 x Ω x [ 1 + (0.00392) × (35 − 0) ] = 113.72 ohms

We should note that the temperature is measured in Celsius in all equations. You can convert Celsius to Fahrenheit using online calculators. Alternatively, you can use this formula: ºF = ( °C × 9/5 ) + 32


Now, you understand the basic principles and formulas for RTD temperature calculation. And make sure to check our online calculator to get precise values for RTD resistance and temperature!

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