ppm/K
part per million per kelvin
Thermal expansion coefficientexact by definition
The part per million per kelvin is 10⁻⁶ /K and is how nearly every materials datasheet states thermal expansion, because the raw SI number is inconveniently small. Aluminium is 23 ppm/K, steel 12, borosilicate glass 3.3, and Invar 1.2.
Watch out: A ppm/K figure is almost always the LINEAR coefficient. Volumetric expansion is three times it for an isotropic solid, and mixing the two is a factor-of-three error that hides well in a spreadsheet.
| 1 ppm/K | 0.000001 1/K |
Solvers that use thermal expansion coefficient