Per Kelvin (K⁻¹)
The reciprocal kelvin (K⁻¹, 1/K) is the SI unit of the coefficient of thermal expansion α: the fractional change in length for each kelvin of temperature change. Carbon steel is about 12 × 10⁻⁶ K⁻¹.
Symbol: K⁻¹ (ASCII: 1/K)
Quantity: coefficient of thermal expansion (α, CTE)
SI relation: K⁻¹ is the coherent SI unit of thermal expansion coefficient.
Derivation: The SI unit of the coefficient of thermal expansion: relative change in length (m/m) per kelvin
Exact: yes, by definition
Same quantity as per degree Celsius (°C⁻¹) : the factor between them is exactly 1.
Typical uses
- Linear expansion ΔL = α L ΔT
- Material property datasheets
- Volumetric expansion of liquids (about 2.1 × 10⁻⁴ K⁻¹ for water at 20 °C)
Convert per kelvin to other units
| Conversion | 1 K⁻¹ equals | Reverse |
|---|---|---|
| per kelvin to ppm per kelvin | 1000000 ppm/K | ppm per kelvin to per kelvin |
| per kelvin to per degree Celsius | 1 °C⁻¹ | per degree Celsius to per kelvin |
| per kelvin to per degree Fahrenheit | 0.5555555556 °F⁻¹ | per degree Fahrenheit to per kelvin |
| per kelvin to ppm per degree Fahrenheit | 555555.5556 ppm/°F | ppm per degree Fahrenheit to per kelvin |
Open the Thermal Expansion Coefficient Converter to convert any value between all units.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 4, degree Celsius.
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Per Kelvin (K⁻¹). Retrieved October 25, 2026, from https://scientificconverters.com/units/per-kelvin/
IEEE
Scientific Converters, "Per Kelvin (K⁻¹)," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/units/per-kelvin/