NTC Thermistor Calculator

About beta-value NTC calculations

R = R₀ × exp(B × (1/T − 1/T₀))

T = 1 / (1/T₀ + ln(R/R₀) / B)

Temperatures are converted to kelvin for the calculation. R₀ is the resistance at the calibration temperature T₀, and B (beta) is the material constant from the datasheet. Switch the mode to find resistance at a target temperature, or the temperature implied by a measured resistance; the tolerance gives the resulting min/max band.

How it works

An NTC (negative temperature coefficient) thermistor is a resistor whose resistance falls as it warms — steeply and predictably. The beta equation describes that curve from a single reference point: R₀ is the resistance at a known temperature T₀ (almost always 25 °C), and the beta constant sets how sharply the resistance drops with heat. A higher beta means a steeper curve and more sensitivity. Because the relationship is exponential, a small temperature change produces a large, easy-to-measure resistance change, which is what makes NTCs popular for cheap, sensitive temperature sensing.

Worked example

A common 10 kΩ NTC (R₀ = 10 kΩ at 25 °C, beta = 3950) heated to 50 °C reads about 4.16 kΩ — its resistance has dropped by more than half for a 25-degree rise. Switch the mode and enter a measured resistance to run it the other way and read out the temperature, which is exactly what a microcontroller does after measuring the thermistor through a divider.

Accuracy and limits

The beta equation is a practical approximation over a limited range — good to roughly ±1 °C near the reference point, drifting further out. For precision sensing across a wide range, use the datasheet resistance table or Steinhart–Hart coefficients instead. To turn the thermistor into a usable voltage for an ADC, pair it with thesensor front-end calculator.