RTD Pt100 / Pt1000 Calculator
Convert RTD resistance to temperature and back for Pt100 and Pt1000 sensors, using the IEC 60751 Callendar-Van Dusen equation. °C, °F, and out-of-range fault checks. Free.
Pt100 resistance reference (IEC 60751, α = 0.00385)
A Pt100 reads exactly 100 Ω at 0 °C and rises about 0.385 Ω per °C. Pt1000 is the same curve scaled ×10 (1000 Ω at 0 °C, ~3.85 Ω/°C), which makes lead-wire resistance a smaller share of the reading.
| Temp (°C) | Pt100 (Ω) | Pt1000 (Ω) |
|---|---|---|
| −200 | 18.52 | 185.2 |
| −100 | 60.26 | 602.6 |
| 0 | 100.00 | 1000.0 |
| 25 | 109.73 | 1097.3 |
| 50 | 119.40 | 1194.0 |
| 100 | 138.51 | 1385.1 |
| 200 | 175.86 | 1758.6 |
| 400 | 247.09 | 2470.9 |
| 600 | 313.71 | 3137.1 |
| 850 | 390.48 | 3904.8 |
Reading looks wrong?
An open RTD element or a broken lead reads as a very high resistance (off the top of the scale); a shorted sensor or lead reads near 0 Ω. A reading that's plausible but off by a fixed amount is usually lead-wire resistance on a 2-wire hookup — switch to a 3- or 4-wire connection to cancel it. For the trade-offs between RTDs and thermocouples and how to wire each, see RTD vs thermocouple: which to use.