Wirecora resistor guide
Resistor Temperature Coefficient Explained
Learn how resistor TCR in ppm/K estimates resistance change with temperature and how the sixth color band differs from ordinary tolerance.
Direct answer: Temperature coefficient of resistance, or TCR, describes how strongly resistance changes as temperature moves away from its reference point. A smaller ppm/K value indicates less permitted change per kelvin.
Band-by-band explanation
- Band 1 · First digitBrown
- Band 2 · Second digitBlack
- Band 3 · Third digitBlack
- Band 4 · MultiplierRed
- Band 5 · ToleranceBrown
- Band 6 · Temperature coefficientBrown
The Brown TCR band is read at the right-hand end. Its temperature coefficient is ±100 ppm/K; the applicable reference temperature comes from the component specification.
How it works
- Find the nominal resistance and the TCR specification in ppm/K, shown by band six when that code is present.
- Measure the temperature difference from the reference condition in kelvins or degrees Celsius; interval sizes are equal.
- Estimate the resistance change with nominal ohms × TCR × temperature change ÷ 1,000,000.
Practical example
A 10 kΩ resistor rated at 50 ppm/K changes by approximately 10,000 × 50 × 40 ÷ 1,000,000 = 20 Ω over a 40 K temperature difference, before other error sources are considered.
Common mistakes
Check these points before relying on a color-code reading or component substitution.
Do not read ppm/K as percent per degree; 10,000 ppm equals one percent.
Do not substitute TCR for tolerance: tolerance covers initial value spread, while TCR describes temperature-related movement.
Related resistor values
Open a worked color-code page generated from the same resistor engine as the calculator.
Related guides
How to Read a 6-Band Resistor Color Code
Understand all six resistor bands: three significant digits, multiplier, tolerance, and temperature coefficient in parts per million per kelvin.
Resistor Tolerance Explained with Practical Ranges
Learn what resistor tolerance means, how to calculate minimum and maximum resistance, and why tolerance is not the same as accuracy in every condition.
Frequently asked questions
Short answers to questions that commonly arise with this resistor topic.
Are kelvin and Celsius changes interchangeable in a TCR calculation?
Yes. A temperature interval of one kelvin has the same size as an interval of one degree Celsius.
Is TCR always shown as a sixth color band?
No. Many resistors have no sixth band; use the manufacturer datasheet when temperature stability matters.
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