NTC Thermistor Calculator
Convert NTC thermistor resistance to temperature and back using the Beta model or the more accurate Steinhart–Hart equation, and calculate Steinhart–Hart coefficients from three calibration points.
Type in either box; the other updates instantly.
Resistance vs temperature for these values
| Temperature | Resistance |
|---|---|
| −40 °C | 401.8597 kΩ |
| −30 °C | 200.2039 kΩ |
| −20 °C | 105.3847 kΩ |
| −10 °C | 58.2457 kΩ |
| 0 °C | 33.6206 kΩ |
| 10 °C | 20.1746 kΩ |
| 20 °C | 12.5353 kΩ |
| 30 °C | 8.0371 kΩ |
| 40 °C | 5.3015 kΩ |
| 50 °C | 3.5882 kΩ |
| 60 °C | 2.4862 kΩ |
| 70 °C | 1.7598 kΩ |
| 80 °C | 1.2703 kΩ |
| 90 °C | 933.577 Ω |
| 100 °C | 697.520 Ω |
| 110 °C | 529.140 Ω |
| 120 °C | 407.089 Ω |
| 130 °C | 317.290 Ω |
| 140 °C | 250.302 Ω |
| 150 °C | 199.682 Ω |
NTC Thermistor Equations
Beta model
The Beta (β) model is the simplest and is what most datasheets quote, for example "10 kΩ, B25/85 = 3950 K".
1/T = 1/T0 + ln(R/R0) ÷ β
T and T0 are in kelvin (°C + 273.15). The Beta model is typically accurate to about ±0.5 °C over a 50 °C span around T0, but error grows further away.
Steinhart–Hart equation
With coefficients fitted from three points, Steinhart–Hart is usually accurate to better than ±0.02 °C across a range of 100 °C or more, which is why precision instruments use it.
Worked example
A 10 kΩ NTC with β = 3950 K at T0 = 25 °C. At 60 °C: R = 10000 × exp(3950 × (1/333.15 − 1/298.15)) = 2486.2 Ω.
Frequently Asked Questions
What does 10K 3950 mean on a thermistor?
It means the resistance is 10 kΩ at 25 °C and the Beta constant is 3950 K. Enter these values in the Beta model tab to get the full resistance curve.
Should I use the Beta or Steinhart–Hart equation?
Use Beta for quick estimates or narrow ranges. Use Steinhart–Hart when you need accuracy over a wide range or when the datasheet gives a resistance table rather than a single Beta.
How do I find Steinhart–Hart coefficients?
Take three resistance values at known temperatures, usually from the manufacturer’s table, and enter them in the Find coefficients tab. The calculator solves for A, B and C.
Why does my thermistor read high temperature when it is cold?
NTC means negative temperature coefficient: resistance goes up as temperature goes down. If the reading moves the wrong way, the input is probably configured for a PTC or RTD.