RTD Resistance to Temperature Calculator (PT100, PT1000)
Convert between temperature and resistance for PT100 and PT1000 platinum RTDs, using the standard IEC 60751 curve.
Sensor
Assumes the standard alpha = 0.00385 curve used by most industrial RTDs.
Temperature to resistance
Resistance to temperature
How it works
A platinum RTD's resistance rises almost linearly with temperature. The IEC 60751 standard defines the exact curve with the Callendar–Van Dusen equation:
T < 0 °C: R = R0 (1 + A·T + B·T² + C·(T − 100)·T³)
A = 3.9083×10⁻³ B = −5.775×10⁻⁷ C = −4.183×10⁻¹²
For temperatures at or above 0 °C the equation is solved exactly for temperature; below 0 °C the calculator solves it numerically.
Worked example
A PT100 at 100 °C has a resistance of 138.51 Ω. A reading of 119.40 Ω corresponds to about 50 °C.
PT100 reference values
| °C | Ω | °C | Ω |
|---|---|---|---|
| −50 | 80.31 | 150 | 157.33 |
| 0 | 100.00 | 200 | 175.86 |
| 50 | 119.40 | 250 | 194.10 |
| 100 | 138.51 | 300 | 212.05 |
Common questions
Does lead wire resistance matter?
Yes. In a two-wire connection the lead resistance adds to the reading and appears as a temperature error. Three- and four-wire connections compensate for it. A PT1000 is less affected because the same lead resistance is a smaller fraction of 1000 Ω.
What about sensor tolerance?
The curve is the ideal one. Real sensors are within a tolerance class (such as Class A or B) of this curve, which is separate from this calculation.
Calculations are provided for convenience and education. Verify results against the sensor datasheet and your measurement system's specifications.