NTC Thermistor Calculator (Beta)
Compute an NTC thermistor's resistance at a temperature, or the temperature from a measured resistance, using the Beta model.
Beta model: 1/T = 1/T₀ + (1/B)·ln(R/R₀), T in kelvin, T₀ = 298.15 K. Accurate to a few °C over 0–100 °C; use Steinhart–Hart for wider ranges.
Disclaimer: This calculator is provided for general informational and educational purposes only, on an “as is” basis and without any warranty of accuracy or fitness for a particular purpose. Results may contain errors — always verify independently before relying on them in real designs. PartAndStock accepts no liability for any loss or damage arising from use of this tool, including when embedded on third-party sites.
How to use
- 1Enter the thermistor's nominal resistance at 25 °C (R₂₅) and the Beta value from its datasheet.
- 2Pick the mode: temperature → resistance, or measured resistance → temperature.
- 3Enter the temperature (°C) or measured resistance (kΩ); the result is computed instantly.
How it works
Enter the nominal resistance (R₂₅) and Beta coefficient to find the resistance at a given temperature, or the temperature from a measured resistance, via the Beta equation.
How the Beta model works
An NTC (Negative Temperature Coefficient) thermistor's resistance falls exponentially as temperature rises. The Beta model approximates this with a single coefficient (B, in kelvin): 1/T = 1/T₀ + (1/B)·ln(R/R₀), where R₀ is the resistance at the reference temperature (T₀ = 25 °C = 298.15 K) and B is the curve coefficient, usually given as B25/85 on the datasheet. Temperatures are used in kelvin.
Accuracy and Steinhart–Hart
The Beta model is accurate to a few °C over a narrow band (0–100 °C); the error grows over wide ranges. For high accuracy, use the three-coefficient Steinhart–Hart equation: 1/T = A + B·ln(R) + C·ln³(R). Also keep the sensing current low when reading the thermistor, or self-heating will bias the measurement.
Worked examples
- R₂₅=10 kΩ, B=3950, T=50 °C → R ≈ 3.60 kΩ
- R₂₅=10 kΩ, B=3950, T=0 °C → R ≈ 27.3 kΩ
- R₂₅=10 kΩ, B=3950, measured 3.6 kΩ → T ≈ 50 °C
10 kΩ / B=3950 NTC — Typical Values
| Temperature | Resistance |
|---|---|
| 0 °C | ~27.3 kΩ |
| 25 °C | 10 kΩ |
| 50 °C | ~3.6 kΩ |
| 85 °C | ~1.07 kΩ |
| 100 °C | ~0.68 kΩ |