Tools

Thermocouple temperature & voltage

Convert between temperature and thermoelectric voltage (mV) for type K, J, T, N, E, and B thermocouples, using the NIST ITS-90 reference functions.

Calculator

Thermocouple converter

Choose a thermocouple type, then enter a temperature or a voltage — the others are calculated automatically.

Temperature —
Temperature —
Thermoelectric voltage —

The thermoelectric voltage is the meter reading for a junction at the shown temperature with the reference (cold) junction held at the temperature you entered. Set the reference junction to 0 °C (the default) to match standard thermocouple tables, or to your ambient/terminal temperature for cold-junction compensation.

Formulas used

  • E(t) = Σ cᵢ × tⁱ — voltage from temperature (t in °C, E in mV, 0 °C reference)
  • Type K above 0 °C adds: + a₀ × e^(a₁ × (t - a₂)²)
  • t = Σ dᵢ × Eⁱ — temperature from voltage (piecewise by voltage sub-range)
  • V_measured = E(t_hot) - E(t_ref) — reference-junction compensation (law of intermediate temperatures)
  • °F = °C × 9/5 + 32

Coefficients are the NIST ITS-90 thermocouple reference functions and inverse functions. Inverse (voltage→temperature) functions carry NIST's stated tolerance of roughly ±0.05 °C.