Pt100 Resistance & Tolerance Calculator
Convert temperature to resistance, resistance to temperature, and check the tolerance of Class A, Class B or AA / 1/3B Pt100 sensors.
How the Pt100 calculator works
The calculator uses the IEC 60751 Callendar–Van Dusen equation. Above 0 °C, the resistance is R = R0 (1 + A t + B t²). Below 0 °C, the C term is included. The resistance-to-temperature direction uses the inverse equation for positive temperatures and a numerical solution below zero.
Accuracy class is shown as the allowed deviation in °C at the calculated temperature, plus the approximate resistance equivalent using the average Pt100 sensitivity of about 0.385 Ω/°C.
When to use it
- Checking a Pt100 reading against a resistance measurement
- Estimating the resistance at a calibration point
- Comparing Class A, Class B and AA / 1/3B tolerances
- Teaching or verifying a transmitter range
For a complete measurement, use a 3- or 4-wire connection and a calibrated instrument. A sensor that is within tolerance at one point can still have a wiring or installation error. See our 2-wire / 3-wire / 4-wire guide and Pt100 probe sensors.
FAQ
What is the formula for a Pt100?
Above 0 °C, R = R0 (1 + A t + B t²) with A = 3.9083 × 10⁻³ and B = −5.775 × 10⁻⁷. Below 0 °C, the Callendar–Van Dusen C term is also used.
What is the difference between Class A and Class B?
Class A tolerance is ±(0.15 + 0.002|t|) °C; Class B is ±(0.30 + 0.005|t|) °C. AA / 1/3B is ±(0.10 + 0.0017|t|) °C.
Does this calculator work for Pt1000?
No — this page is for Pt100. For Pt1000, the resistance values are ten times higher; contact us if you need a Pt1000 version.
Why does my measured resistance not match?
Check the wiring (2/3/4-wire), cable resistance, sensor tolerance and the actual temperature. A 3- or 4-wire measurement is recommended for accuracy.