per kelvin
Thermal expansion coefficientexact by definition
The reciprocal kelvin is the SI unit of the thermal expansion coefficient: the fractional change in length, area or volume per kelvin of temperature change. Because it is a fraction divided by a temperature interval, it is dimensionally an inverse temperature, and its factor of 1 is exact. Steel is about 12e-6 per kelvin, copper 16.5e-6, aluminium 23e-6 and PVC 50 to 80e-6.
Watch out: Linear and volumetric coefficients share this unit and differ by a factor of three for an isotropic material, since a solid expands in all three directions at once. Water's volumetric coefficient near 20 °C is about 207e-6 per kelvin, and it goes negative below 4 °C, which is why ice floats and why lakes freeze from the top.
| 1 | 1 |
One per kelvin in every thermal expansion coefficient unit
| 1,000,000 | part per million per kelvin (ppm/K) | |
| 1,000,000 | part per million per Celsius degree (ppm/°C) | |
| 555,556 | part per million per Fahrenheit degree (ppm/°F) | |
| 555,556 | microinch per inch per Fahrenheit degree (μin/(in·°F)) | |
| 100 | percent per Celsius degree (%/°C) | |
| 55.5556 | percent per Fahrenheit degree (%/°F) | |
| 1 | per kelvin (1/K)this unit | |
| 1 | per Celsius degree (1/°C) | |
| 0.555556 | per Fahrenheit degree (1/°F) | |
| 0.555556 | per Rankine degree (1/°R) |