What resistance is a Pt100 at 0°C?

A nominal Pt100 is 100 ohms at 0°C; a Pt1000 is 1000 ohms at 0°C.

Which RTD curve does this calculator use?

It uses IEC 60751 alpha 0.00385 Callendar–Van Dusen coefficients from -200°C to 850°C.

Does this correct lead-wire resistance?

No. Correct two-, three- or four-wire measurement effects before using the resistance value.

Can this replace RTD calibration?

No. Sensor tolerance, self-heating, transmitter and measurement uncertainty remain separate.

Pt100/Pt1000 RTD Resistance to Temperature Calculator

Convert platinum RTD resistance and temperature in either direction using the bounded IEC 60751 α=0.00385 curve.

About this calculator

Quick Calculator inputs above give an instant result; use Advanced fields (factors, units, or decoding) when your datasheet differs from defaults.

Example: Pt100 at 100 °C ≈ 138.51 Ω (IEC 60751 Callendar–Van Dusen).

Result explanation / How to use: treat values as screening only. Engineering assumption and disclaimer: confirm nameplate limits, OEM selectors, and site conditions before procurement or programming.

Hub: Protection calculators — continue related sizing from this topic cluster.

RTD conversion

Direction

RTD nominal type

R0 at 0°C (Ω)

Temperature (°C)

RTD result

Formula and boundary:

Correct lead-wire resistance and account for sensor class, transmitter error, self-heating and calibration uncertainty separately. Do not extrapolate outside the stated curve.

PLC analog scaling → PLC diagnostics →

Your Calculation Path

rtd resistance temperatureScale PLC analog input →

Continue Your Calculation

Convert the transmitter output to engineering units and verify the PLC channel configuration.

Callendar–Van Dusen method

The positive-temperature branch uses A and B; the sub-zero branch adds C(T−100)T³. The inverse is solved only inside −200°C to 850°C.

Primary reference: NIST/BIPM Guide on Secondary Thermometry for Industrial Platinum Resistance Thermometers.

Frequently Asked Questions

What is Pt100 resistance at 100°C?

For the IEC α=0.00385 curve it is approximately 138.5055 Ω.

Can I use a custom R0?

Yes, but the A/B/C curve remains IEC α=0.00385; this is not custom sensor calibration.

Why is the sub-zero equation different?

The C coefficient improves the platinum curve below 0°C.

Why is my measured value different?

Lead resistance, tolerance class, self-heating and instrumentation uncertainty can all contribute.