Calculator Inputs
Formula Used
This linear model estimates resistance at a target temperature from a known reference resistance and temperature coefficient.
Use this form when you know both resistances and both temperatures, and you want the coefficient.
Use this to recover the reference resistance needed to reach a target resistance at a chosen operating temperature.
When alpha is entered in ppm/°C, the calculator converts it internally using: α(1/°C) = α(ppm/°C) ÷ 1,000,000. The linear model works best near the reference temperature and over moderate ranges.
How to Use This Calculator
- Select the calculation mode based on the value you want to solve.
- Enter resistance values in ohms and temperatures in your preferred units.
- Choose alpha units as ppm/°C or 1/°C.
- Set a chart range to visualize resistance behavior over temperature.
- Click Calculate Now to show the result under the header and above the form.
- Use the export buttons to save a CSV summary or a PDF report.
Example Data Table
| Example | Reference Resistance (Ω) | Alpha (ppm/°C) | Reference Temp (°C) | Target Temp (°C) | Calculated Target Resistance (Ω) |
|---|---|---|---|---|---|
| Platinum RTD style example | 100 | 3850 | 20 | 80 | 123.1 |
| Low-drift precision resistor | 1000 | 25 | 25 | 75 | 1001.25 |
| Negative coefficient device | 10000 | -4000 | 25 | 60 | 8600 |
Frequently Asked Questions
1. What is the temperature coefficient of resistance?
It shows how much a resistor’s value changes for each degree of temperature change. Positive values mean resistance rises with temperature. Negative values mean it falls.
2. What does ppm/°C mean?
It means parts per million per degree Celsius. A value of 100 ppm/°C changes resistance by 0.01% for every 1°C change from the reference temperature.
3. Why is the reference temperature important?
The linear model compares all changes to a starting point. If the reference temperature is wrong, the predicted resistance shift will also be wrong.
4. Can the temperature coefficient be negative?
Yes. Some materials and thermistors have negative coefficients. In those cases, resistance decreases as temperature increases, which this calculator can model directly.
5. Is this calculator accurate for very large temperature ranges?
It uses a linear approximation, so it is best for moderate ranges near the reference point. For wide ranges, a nonlinear material model may be more accurate.
6. Which calculation mode should I choose?
Use target resistance mode when alpha is known. Use alpha mode when you have measured resistance values. Use reference resistance mode when you know the operating resistance and need the baseline value.
7. Does the graph use the same formula as the result?
Yes. The chart applies the same linear resistance equation across the selected temperature range, so the curve matches the current calculation setup.
8. Can I use Fahrenheit or Kelvin temperatures?
Yes. The calculator accepts Celsius, Fahrenheit, and Kelvin. It converts them internally so the result and graph stay consistent with the linear coefficient formula.