PT100 / PT1000 RTD Calculator (IEC 60751)

What this tool does

Platinum resistance thermometers change by about 0.385 Ω per °C (for a PT100), slightly less as the temperature rises — the Callendar–Van Dusen equation with the standard IEC 60751 coefficients captures that curvature, adding an extra term below 0 °C. A PT100 reads 100 Ω at 0 °C and about 138.5 Ω at 100 °C. Because the change per degree is small, lead-wire resistance matters: use a 3- or 4-wire connection for anything precise. The reverse calculation here is for 0 °C and above.

Formula

R(T) = R₀(1 + A T + B T²) for T ≥ 0 · + C (T − 100) T³ below 0 °C (IEC 60751: A = 3.9083×10⁻³, B = −5.775×10⁻⁷, C = −4.183×10⁻¹²)

Variables

Worked example

Limitations

• For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.
• Coverage and consumption figures vary between products. Take the values from the manufacturer's datasheet for the product you are actually using.