Thermocouple & PT100 Converter
For engineers and technicians: convert between temperature and PT100/PT1000 resistance or type K thermocouple voltage.
How to use the Thermocouple & PT100 Converter
- Choose the sensor type.
- Choose temperature → signal or signal → temperature.
- Enter the value in °C, ohms or millivolts.
How it works
Platinum RTDs follow the Callendar–Van Dusen equation (IEC 60751): R(T) = R₀(1 + AT + BT²) above 0 °C, with an extra C(T − 100)T³ term below 0 °C, where A = 3.9083 × 10⁻³, B = −5.775 × 10⁻⁷ and C = −4.183 × 10⁻¹². A PT100 reads 100 Ω at 0 °C and 138.51 Ω at 100 °C.
Type K thermocouple values are interpolated from NIST ITS-90 reference points every 100 °C with the reference junction at 0 °C; use full NIST tables for calibration-grade work.
PT100 resistance table
| °C | PT100 (Ω) | PT1000 (Ω) |
|---|---|---|
| -100 | 60.256 | 602.56 |
| -50 | 80.306 | 803.06 |
| 0 | 100 | 1,000 |
| 25 | 109.735 | 1,097.35 |
| 50 | 119.397 | 1,193.97 |
| 100 | 138.506 | 1,385.06 |
| 200 | 175.856 | 1,758.56 |
| 300 | 212.052 | 2,120.52 |
| 500 | 280.978 | 2,809.78 |
Frequently asked questions
What is the resistance of a PT100 at 0 °C?
Exactly 100 Ω.
How much does a PT100 change per degree?
About 0.385 Ω per °C near room temperature.
What is the range of a type K thermocouple?
About −200 °C to 1,260 °C continuous (up to 1,372 °C short term).
Why use an RTD instead of a thermocouple?
RTDs are more accurate and stable at moderate temperatures; thermocouples handle much higher temperatures and are cheaper.