Convert Triple Point of Water (TPW) to Kelvin (K) instantly.
About these units
Triple Point of Water (TPW)
The Triple Point of Water (TPW) is not a temperature scale but a defining thermodynamic condition where water exists simultaneously as solid, liquid, and vapor. This state occurs at a very precise temperature: 273.16 K (0.01°C) under a pressure of 611.657 pascals. The TPW was historically crucial because the kelvin was directly defined using this temperature. Prior to the 2019 SI redefinition, the triple point of water served as the anchor for the absolute temperature scale and was used to calibrate thermometers worldwide. This made high-precision thermometry simpler, as laboratories could reproduce the TPW by using sealed cells filled with highly pure water. Even though the kelvin is now defined through Boltzmann's constant, the TPW remains essential in metrology because it is one of the most reproducible physical phenomena known. Standard cells are still used for calibrations, research, and quality control in temperature-sensitive industries. The TPW embodies the elegance of thermodynamics: a single point where phase equilibrium meets the foundations of measurement.
Kelvin (K)
The kelvin is the base unit of temperature in the International System of Units (SI) and is unique among temperature scales because it begins at absolute zero, the theoretical point where all classical molecular motion ceases. This gives the kelvin an absolute physical foundation that other temperature scales lack. Instead of being tied to the properties of water or human experience, the kelvin reflects universal thermodynamic behavior, making it indispensable for physics, chemistry, engineering, and cosmology. One of the kelvin's strengths is that temperature differences measured in kelvins are identical to those measured in degrees Celsius, simplifying conversions in scientific work. The kelvin scale is critical for understanding entropy, thermal energy, and statistical mechanics, where temperature represents average kinetic energy of particles rather than subjective sensation. Modern definitions anchor the kelvin to a fixed numerical value of the Boltzmann constant, connecting macroscopic temperature directly to microscopic energy. This reformulation, adopted in 2019, ensures that the kelvin remains precise and universally stable across laboratories worldwide, independent of any specific material reference point. As such, the kelvin is not merely a unit of temperature—it is a gateway to the deeper physical meaning of heat and energy.