Callendar–Van Dusen conversion between RTD resistance and temperature (IEC 60751).

Callendar–Van Dusen equation

Platinum RTDs per IEC 60751 follow

R (t) = R_{0} (1 + A t + B t^{2}) (t \geq 0^{\circ} C)

R (t) = R_{0} (1 + A t + B t^{2} + C (t - 100) t^{3}) (t < 0^{\circ} C)

with A = 3.9083×10⁻³, B = −5.775×10⁻⁷, C = −4.183×10⁻¹² and R₀ = 100 Ω (PT100) or 1000 Ω (PT1000). This tool inverts the equation numerically, so it is valid over the full −200 to +850 °C span. Remember that lead-wire resistance adds directly to a 2-wire measurement — use 3- or 4-wire connections for accuracy.

PT100 / PT1000 Calculator

Callendar–Van Dusen equation