From 0 to 850 °C
R(t) = R₀ (1 + At + Bt²)
Pt100 / Pt1000 Calculator
Convert RTD temperature to resistance, or resistance to temperature, using the IEC 60751 nominal platinum curve. Supports Pt100, Pt1000, Celsius and Fahrenheit, including temperatures below zero.
Curve range: −200 to 850 °C. Your probe may have a narrower rating.
Switch units without changing the temperature.
IEC 60751 · α ≈ 0.00385
Nominal element resistance. Lead resistance, calibration corrections and sensor tolerance are not included.
Try an example:
Calculated Pt100 resistance
Ω
R = R₀ (1 + At + Bt²)
Complete the input to see the corresponding point on the curve.
Pt100 · IEC 60751 nominal curve · α ≈ 0.00385
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Send your result with the part number, required range and wiring details.
Your sensor type, input and result will be included when the calculator is enabled.
What resistance should a Pt100 or Pt1000 read?
A nominal Pt100 reads 100 Ω at 0 °C and approximately 138.51 Ω at 100 °C. A Pt1000 reads 1000 Ω at 0 °C and approximately 1385.06 Ω at 100 °C. These values use the IEC 60751 platinum curve (α ≈ 0.00385). Pt1000 resistance is ten times Pt100 resistance at the same temperature on this curve.
Resistance increases with temperature, but the relationship is not exactly linear. This calculator uses the Callendar–Van Dusen equation over −200 to 850 °C (−328 to 1562 °F), with an additional term below 0 °C. That is the calculation range, not a guarantee of your probe's operating range.
Pt100 resistance formula and coefficients
From −200 to below 0 °C
R(t) = R₀ [1 + At + Bt² + C(t − 100)t³]
t is temperature in °C and R(t) is resistance in ohms. R₀ is 100 Ω for Pt100 or 1000 Ω for Pt1000. Fahrenheit values are converted with t = (°F − 32) × 5 ÷ 9 before applying the equation.
A = 3.9083 × 10⁻³ °C⁻¹
B = −5.775 × 10⁻⁷ °C⁻²
C = −4.183 × 10⁻¹² °C⁻⁴
For resistance-to-temperature conversion, the calculator numerically solves the same curve within its stated range. Values outside that range are rejected rather than extrapolated. Results describe a nominal sensor; displayed decimal places do not represent measurement accuracy.
Worked RTD conversion examples
Pt100 at 100 °C: R = 100 × [1 + (3.9083 × 10⁻³ × 100) − (5.775 × 10⁻⁷ × 100²)] = 138.5055 Ω.
Pt100 at −50 °C: including the below-zero C term gives approximately 80.3063 Ω. A Pt1000 at the same temperature is approximately 803.0628 Ω.
Pt100 reading 100 Ω: the nominal temperature is 0 °C or 32 °F. Selecting Pt1000 for a 100 Ω reading produces an out-of-range result; check the sensor type before interpreting a measurement.
Pt100 / Pt1000 resistance table
Selected nominal values are listed below. Download the complete reference table at 10 °C intervals; it includes both sensor types and both temperature units.
−200 to 850 °C · 106 temperature rows
| °C | °F | Pt100 Ω | Pt1000 Ω |
|---|---|---|---|
| −200 | −328 | 18.5201 | 185.2008 |
| −100 | −148 | 60.2558 | 602.5584 |
| −50 | −58 | 80.3063 | 803.0628 |
| 0 | 32 | 100.0000 | 1000.0000 |
| 25 | 77 | 109.7347 | 1097.3466 |
| 100 | 212 | 138.5055 | 1385.0550 |
| 200 | 392 | 175.8560 | 1758.5600 |
| 500 | 932 | 280.9775 | 2809.7750 |
| 850 | 1562 | 390.4811 | 3904.8113 |
Common Pt100 and Pt1000 questions
Does 2-wire, 3-wire or 4-wire wiring change this calculation?
The nominal element curve stays the same. A two-wire measurement includes the resistance of both leads, which can make the indicated temperature too high. Three-wire compensation depends on the measurement circuit and matched lead resistances. A four-wire measurement separates current and voltage connections to reduce lead-resistance error. This calculator does not correct a raw reading for wiring resistance.
Can I use this for a different RTD curve or a calibrated probe?
This tool uses the nominal IEC 60751 platinum curve with α approximately 0.00385. It does not support nickel or copper RTDs, platinum curves such as α 0.00392, or an individual probe's calibration coefficients. Use the sensor data sheet or calibration certificate when those apply.
Can every Pt100 probe operate from −200 to 850 °C?
No. The permitted temperature range depends on the element construction, probe assembly, insulation, cable and accuracy class. Check the complete probe's data sheet. This tool's mathematical range does not establish the probe's rating.
How do I convert a Pt100 measurement to 4–20 mA?
An RTD resistance and a transmitter's current output are different signals. First convert the resistance to temperature here. Then use the transmitter's configured lower and upper temperature limits in the 4–20 mA signal converter. The current depends on that configured range.
Is an out-of-range resistance proof that the sensor has failed?
No. It may indicate the wrong sensor type, an unsupported curve, a wiring problem, an open or short circuit, or a temperature outside this tool's range. Verify the sensor specification and measurement setup before drawing a conclusion.
Calculation basis and sources
The coefficients, equations and wiring considerations are documented in Texas Instruments' A Basic Guide to RTD Measurements, sections 1.1 and 1.3, and PR electronics' RTD temperature sensor guide.
The calculator and reference table apply the nominal curve; they do not certify a sensor or replace its calibration. Formula and example review: .