NTC Thermistor Calculator
Calculate resistance from temperature or temperature from resistance using the Beta model. ADC voltage divider output.
NTC Parameters
Voltage Divider (for ADC)
Results
Enter valid component values.
R(T) = R₀ × e^(B × (1/T − 1/T₀))
NTC Thermistors Explained
An NTC (Negative Temperature Coefficient) thermistor is a resistor whose resistance decreases as temperature increases. The relationship is exponential, not linear: a 10kΩ NTC might measure 30kΩ at 0°C and 4kΩ at 50°C. The Beta equation R(T) = R₀ × e^(B×(1/T − 1/T₀)) models this behavior with reasonable accuracy over a typical range of −20°C to 120°C.
The Beta coefficient (B value) characterizes the steepness of the R-T curve. Common NTC thermistors have B values between 3000K and 4500K. A higher B means the resistance changes more sharply with temperature — better sensitivity but also more nonlinearity. For the most accurate readings, use a lookup table or the Steinhart-Hart equation (three coefficients) instead of the simplified Beta model.
To read an NTC with a microcontroller, connect it in a voltage divider with a fixed resistor. The ADC reads a voltage that depends on the thermistor's resistance. Choose the fixed resistor equal to R₀ (the resistance at the midpoint of your temperature range) for the best resolution. A 10kΩ NTC with a 10kΩ fixed resistor gives good sensitivity around room temperature.
Beta Equation
R(T) = R₀ × e^(B × (1/T − 1/T₀))Key Points
- NTC: resistance decreases with temperature (negative coefficient)
- PTC: resistance increases with temperature (positive coefficient)
- Beta equation accuracy: ±1°C over −20°C to 100°C range
- Use series resistor ≈ R₀ for best ADC resolution at midrange
Applications
- Temperature measurement with Arduino/ESP32
- HVAC and climate control systems
- Battery temperature monitoring
- Inrush current limiting (NTC power thermistors)