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RTD Pt100 / Pt1000 Calculator

Convert between resistance and temperature for Pt100, Pt500 and Pt1000 sensors across the full −200 to +850 °C RTD range. Supports IEC 60751, JIS C1604 and US industrial standards using the Callendar–Van Dusen equation.

Quick Presets

Input

Valid range: −200 to +850 °C

 

Resistance

109.735
Ω
SensorPt100
StandardIEC 60751
Deviation vs R₀+9.735 Ω
Class A tolerance±0.20 °C

Pt100 / Pt500 / Pt1000 Reference Table

All values use the IEC 60751 curve (α = 0.003851) — the global baseline for industrial RTDs and the default coefficient used by HM Sensor temperature transmitters.

Temp (°C)Pt100 (Ω)Pt500 (Ω)Pt1000 (Ω)Class A (°C)Class B (°C)
-20018.52092.600185.201±0.55±1.30
-10060.256301.279602.558±0.35±0.80
-5080.306401.531803.063±0.25±0.55
0100.000500.0001000.000±0.15±0.30
25109.735548.6731097.347±0.20±0.42
50119.397596.9861193.971±0.25±0.55
100138.505692.5271385.055±0.35±0.80
150157.325786.6261573.251±0.45±1.05
200175.856879.2801758.560±0.55±1.30
300212.0511060.2572120.515±0.75±1.80
500280.9781404.8882809.775±1.15±2.80
700345.2841726.4183452.835±1.55±3.80
850390.4811952.4063904.811±1.85±4.55

How to Use This RTD Calculator

This calculator inverts the Callendar–Van Dusen equation in both directions, with Newton–Raphson iteration for sub-zero temperatures. It is useful for commissioning, calibration verification, and troubleshooting RTD loops in the field.

Step 1: Pick the sensor type — Pt100, Pt500 or Pt1000. The difference is only the nominal R₀ value; the curve shape is identical.

Step 2: Pick the standard. Default to IEC 60751 (α = 0.003851) for all modern industrial sensors and for HM Sensor HE-series temperature transmitters. Only select JIS or US if you are matching legacy hardware.

Step 3: Choose the conversion direction. Temperature → Resistance is what you need when sizing a sensor or specifying a calibration target. Resistance → Temperature is what you need when verifying a multimeter reading from a field probe.

Step 4: Enter the value. The result updates instantly. The output panel shows the converted value, the deviation from R₀, and the Class A tolerance at that temperature.

Quick Presets: Use the preset buttons to load common commissioning scenarios — ambient, boiling point, cryogenic, and high-temperature baseline values.

Callendar–Van Dusen Formula

RTD resistance is a non-linear function of temperature. All major standards describe it with the same polynomial form; only the A, B, C coefficients differ.

RangeEquation
t ≥ 0 °CR(t) = R₀ · (1 + A·t + B·t²)
t < 0 °CR(t) = R₀ · (1 + A·t + B·t² + C·(t−100)·t³)

Standard Coefficients

Standardα (°C⁻¹)ABC (t < 0)
IEC 60751 / DIN 437600.0038513.9083×10⁻³−5.775×10⁻⁷−4.183×10⁻¹²
JIS C1604-19810.0039163.9739×10⁻³−5.870×10⁻⁷−4.400×10⁻¹²
US Industrial0.0039263.9848×10⁻³−5.870×10⁻⁷−4.000×10⁻¹²

Inverting the equation above 0 °C is a quadratic solve. Below 0 °C the cubic correction term makes analytical inversion impractical — this calculator uses Newton–Raphson iteration starting from the quadratic approximation, converging within 3–5 iterations to better than 1 × 10⁻⁷ °C precision.

4-20mA Signal Calculator

Convert between mA current signals, process values, and percentage of range — ideal companion once you have specified your temperature transmitter range.

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Instantly convert between 15 pressure units — Pa, kPa, MPa, bar, PSI, atm, mmHg, inH₂O and more — for transmitter range specification.

HM100 Temperature Transmitter with RTD input

HM100 Integrated Temperature Transmitter

Universal RTD / TC input, 4-20mA output

  • RTD input: Pt100 / Pt500 / Pt1000 / Cu50 (IEC 60751)
  • Accuracy: ±0.1% of span, Class A or better
  • Output: 4-20mA 2-wire, 10-36 VDC loop
  • Options: Explosion-proof Ex d IIC T6, HART
View Full Specs Get a Quote
SBW Temperature Transmitter

SBW Head-Mount Temperature Transmitter

Compact head-mounted Pt100 transmitter

  • Mount: DIN B head inside sensor housing
  • Input: Pt100 (2/3/4-wire), thermocouple options
  • Output: 4-20mA 2-wire, field re-ranging available
  • Use case: Pair with any RTD probe + thermowell
View Full Specs Get a Quote

Frequently Asked Questions

Pt100 is a platinum resistance thermometer with a nominal resistance of exactly 100 Ω at 0 °C. Its resistance rises roughly 0.385 Ω per °C under the IEC 60751 curve. Pt500 and Pt1000 follow the same curve scaled by 5× and 10× — use Pt1000 for long cable runs because lead-wire error is proportionally 10× smaller.

Three likely causes: lead-wire resistance in a 2-wire configuration (add ~0.05 Ω per meter per conductor for 24 AWG copper — this offsets the reading by several degrees), sensor self-heating under excessive excitation current, or drift from repeated thermal cycling. Rule out lead-wire error first by switching to a 3- or 4-wire connection, or step up to Pt1000 to shrink the relative effect.

No. α = 0.003851 °C⁻¹ is defined by IEC 60751 as the average resistance slope between 0 °C and 100 °C — not the instantaneous slope at any point. The true response is non-linear, which is why the Callendar–Van Dusen polynomial uses three coefficients (A, B, C) to describe it across the full range.

Class A: ±(0.15 + 0.002·|t|) °C. Class B: ±(0.30 + 0.005·|t|) °C. At 100 °C this means ±0.35 °C for Class A versus ±0.80 °C for Class B. Class A costs more but is worth it for custody transfer, pharmaceutical CIP/SIP cycles, or anywhere a 1 °C error would fail compliance. Class B is sufficient for most HVAC and general process control.

Yes. Once a sensor is calibrated to IEC 60751, the resistance–temperature relationship is identical. The physical difference is reliability: thin-film elements are cheaper and have faster thermal response but drift more under thermal cycling; wire-wound elements hold calibration longer in harsh environments and are the choice for high-accuracy process transmitters.

For most industrial loops, look for a transmitter that accepts Pt100 / Pt1000 input with on-board IEC 60751 linearization, provides a 4-20 mA or HART output, and offers at least Class A accuracy with galvanic isolation. HM Sensor HE-series temperature transmitters cover Pt100/Pt500/Pt1000 and major thermocouple types with Class A linearization built in.

Need Help with Your RTD / Pt100 Application?

Our engineers can recommend the right Pt100 / Pt1000 probe, thermowell and 4-20 mA transmitter for your process — including Class A matched-pair calibration where accuracy matters. Typical response within 12 business hours.
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