Pt100 / Pt1000 Resistance Calculator

How to use this calculator

Choose the sensor type, then type either a temperature to get the expected resistance, or a resistance reading from your multimeter to get the temperature. Temperatures can be entered in °C, °F or K.

The formula (IEC 60751)

For 0 °C ≤ T ≤ 850 °C, platinum RTDs follow the Callendar–Van Dusen equation:

R = R₀ × (1 + A·T + B·T²)

• R₀ — resistance at 0 °C (100 Ω for Pt100)
• A = 3.9083 × 10⁻³ °C⁻¹
• B = −5.775 × 10⁻⁷ °C⁻²
• T — temperature in °C

Worked example

A Pt100 at 100 °C:

R = 100 × (1 + 0.39083 − 0.005775) = 138.51 Ω

Going the other way, a reading of 138.50 Ω means about 99.99 °C.

Pt100 quick table

°C	Pt100 (Ω)	Pt1000 (Ω)
0	100.00	1000.0
50	119.40	1194.0
100	138.51	1385.1
200	175.86	1758.6
300	212.05	2120.5
400	247.09	2470.9

Field tips

• Check for lead resistance. On a 2-wire Pt100, every 1 Ω of cable resistance reads as about 2.6 °C too high.
• Self-heating. Too much measuring current warms the sensor. Typical transmitters use 1 mA or less.
• Tolerance classes. Class A is ±(0.15 + 0.002·|T|) °C; Class B is ±(0.3 + 0.005·|T|) °C.

Frequently asked questions

What is the resistance of a Pt100 at 100 °C?

About 138.51 Ω. A Pt100 is 100 Ω at 0 °C and rises by roughly 0.385 Ω per °C.

What is the difference between Pt100 and Pt1000?

A Pt1000 has ten times the resistance (1000 Ω at 0 °C). It is less affected by lead-wire resistance, so it suits 2-wire connections and battery-powered devices.

Does this work below 0 °C?

This calculator uses the IEC 60751 equation for 0 to 850 °C. Below 0 °C an extra term is needed; support for negative temperatures will be added.

What do 2-wire, 3-wire and 4-wire mean?

They are ways of connecting the RTD. 3-wire and 4-wire connections cancel the resistance of the cable, which otherwise reads as extra temperature.

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