NTC Thermistor Divider Calculator
Calculate NTC thermistor resistance, voltage divider output, ADC reading, temperature from ADC value and best fixed resistor using the Beta formula.
⚡ Maker Rule: For best ADC sensitivity, the fixed resistor is often chosen close to the thermistor resistance near the temperature range you care about. Use this with the ADC Resolution Calculator, Arduino ADC Calculator, Voltage Divider Calculator and future Pull-up Resistor Calculator.
🌡️ NTC Thermistor Voltage Divider — Temperature to ADC
Supply / ADC Reference Voltage
Fixed Resistor
NTC Nominal Resistance R25
Beta Value
Temperature
ADC Bits
Divider Orientation
Common Arduino wiring: fixed resistor to VCC and NTC to ground. In that case Vout falls as temperature rises.
Presets:10k NTC100k NTChot 60°C
ADC Reading
ADC Bits
Supply / ADC Reference
Fixed Resistor
NTC R25
Beta Value
Divider Orientation
This converts ADC code back to resistance and then temperature using the Beta equation.
Target Temperature
NTC R25
Beta Value
Preferred Series
For best sensitivity near a target temperature, choose the fixed resistor close to the NTC resistance at that temperature.
📐 Formula Reference
NTC Beta Formula
R = R25 × e^(β × (1/T − 1/T25))
Divider, NTC Bottom
Vout = Vcc × Rntc ÷ (Rfixed + Rntc)
ADC Code
ADC = Vout ÷ Vref × (2^bits − 1)
Temperature from Resistance
T = 1 ÷ (1/T25 + ln(R/R25)/β)
📋 Quick Reference
Common NTC Values
Arduino modules10k
3D printer hotend100k
Typical beta3950
Wiring Effect
NTC to GNDV falls hot
NTC to VCCV rises hot
Rfixed ≈ Rntcsensitive
Design Checks
ADC referencesame V
Self heatingavoid
Calibrationneeded
📚 Engineering Notes
NTC resistance falls with temperatureAn NTC thermistor has high resistance when cold and lower resistance when hot.
Divider orientation changes ADC directionIf the NTC is at the bottom, ADC voltage falls as temperature rises. If it is at the top, ADC voltage rises as temperature rises.
Beta formula is an approximationFor better accuracy, use a Steinhart-Hart equation or calibration table from the thermistor datasheet.
ADC resolution mattersUse the ADC Resolution Calculator and Arduino ADC Calculator to check voltage step size.
What is an NTC Thermistor Divider Calculator?
An NTC thermistor divider calculator converts temperature to thermistor resistance, voltage divider output and ADC reading. It also converts ADC reading back to temperature using the Beta equation.
How an NTC divider works
The NTC thermistor and a fixed resistor form a voltage divider. As temperature changes, NTC resistance changes, which changes the ADC input voltage.
Choosing the fixed resistor
For good sensitivity, choose the fixed resistor close to the NTC resistance at the temperature range you care about. A 10k NTC often uses a 10k fixed resistor for general room-temperature sensing.
Important limitation
This calculator uses the Beta formula. Real thermistors have tolerance, self-heating, ADC error, reference voltage error and curve nonlinearity. For accurate measurement, calibrate with known temperatures.
❓ Frequently Asked Questions
A 10k NTC thermistor has about 10,000 ohms resistance at 25°C. Its resistance decreases as temperature increases.
For general temperature sensing around room temperature, 10k is commonly used. For another target range, choose a resistor close to the NTC resistance at that temperature.
The divider orientation controls whether ADC voltage rises or falls with temperature. Swap the orientation setting or adjust your code formula.