Thermistor Resistance Calculator
An NTC thermistor's resistance falls as it heats up, following an exponential relationship in absolute temperature. The Beta (B-parameter) model predicts the resistance at any temperature from three datasheet values: the reference resistance, the reference temperature, and the material constant Beta. This calculator takes those values plus a target temperature in Celsius, converts to kelvin, and returns the resistance. Because Beta, R0, and T0 differ for every part, they are entered as user inputs from your thermistor's datasheet. Use it to design temperature-sensing dividers, set firmware lookup points, and verify readings.
Thermistor Beta formula
T (K) = target temp (C) + 273.15
T0 (K) = reference temp (C) + 273.15
R = R0 * exp(B * (1/T - 1/T0))
ratio = R / R0
B is the material constant in kelvin from the datasheet. Temperatures are absolute (kelvin) inside the formula. For an NTC thermistor, R falls as the temperature rises above the reference.
Using the result
- Take R0, T0, and Beta from your specific thermistor datasheet.
- NTC means resistance drops as temperature rises.
- The Beta model is a good approximation over a moderate temperature span.
- For wide ranges, the Steinhart-Hart equation is more accurate.
- Celsius inputs are converted to kelvin by adding 273.15.
Thermistor resistance: frequently asked questions
What is the Beta equation for an NTC thermistor?
The Beta (B-parameter) model is R = R0 * exp(B * (1/T - 1/T0)), where R0 is the resistance at the reference temperature T0, B is the material constant in kelvin, and T and T0 are absolute temperatures in kelvin. It gives the resistance R at temperature T.
Why must temperatures be in kelvin?
The Beta equation is derived from an exponential relationship in absolute temperature, so both T and T0 must be in kelvin (degrees Celsius plus 273.15). This calculator accepts Celsius for convenience and converts to kelvin before applying the formula.
What is a typical Beta value and reference resistance?
A common NTC thermistor is specified as 10,000 ohms at 25 degrees Celsius with a Beta of about 3,950 kelvin, but these vary by part. Always take B, R0, and T0 from the manufacturer datasheet for your specific thermistor; they are entered here as user inputs.
Does this model the full thermistor curve accurately?
The Beta model is a good two-point approximation over a moderate temperature span. For wide ranges and high accuracy, the three-coefficient Steinhart-Hart equation fits better. The Beta equation is the standard quick estimate used in most datasheets and firmware.
What does NTC mean?
NTC stands for negative temperature coefficient: the resistance falls as temperature rises. The Beta equation here models NTC behaviour, which is why a higher temperature than the reference gives a lower resistance, and a lower temperature gives a higher resistance.
Official sources
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.