Triple point of water to Celsius
TPW
°C
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
1 TPW (Triple point of water) → 0.01000038351664053846 °C (Celsius) Just now |
Quick Reference Table (Triple point of water to Celsius)
| Triple point of water (TPW) | Celsius (°C) |
|---|---|
| 0 | -273.15 |
| 0.9999 | -0.0173156165217111256 |
| 1 | 0.01000038351664053846 |
| 1.073 | 19.95068041151335529776 |
| 1.136 | 37.15976043567490365169 |
| 1.366 | 99.98656052388373097553 |
About Triple point of water (TPW)
The triple point of water is a fundamental thermometric reference: the unique temperature and pressure (273.16 K, 611.657 Pa) at which water coexists simultaneously as solid, liquid, and vapor. When used as a temperature unit, one triple-point unit (TPW) equals 273.16 K, so temperatures are expressed as multiples of this fixed point. This makes 0 TPW equal to absolute zero and 1.000 TPW equal to water's triple point exactly. The freezing point (273.15 K) is 0.9999 TPW — just below 1 — while boiling (373.15 K) is approximately 1.366 TPW. This unit served as the defining reference for the kelvin from 1954 until the 2019 SI revision.
Used in metrology laboratories to calibrate precision thermometers. A sealed triple-point cell containing ultra-pure water held at exactly 273.16 K (0.01°C) serves as a primary temperature standard.
About Celsius (°C)
Celsius (°C) is the most widely used temperature scale in the world, adopted by every country except the United States, Liberia, and Myanmar for everyday and scientific use. Zero degrees Celsius is defined as the freezing point of water at standard atmospheric pressure; 100°C is the boiling point. Originally called centigrade because of its 100-degree span between these two reference points, it was renamed Celsius in 1948 to honor Swedish astronomer Anders Celsius. It is the practical temperature scale for weather, cooking, medicine, and most scientific work outside thermodynamics. Body temperature is 37°C; a comfortable room is typically 20–22°C.
Water freezes at 0°C and boils at 100°C. Normal human body temperature is 37°C. A warm summer day in southern Europe is around 35°C.
Etymology: Named after Swedish astronomer Anders Celsius (1701–1744), who proposed a 100-degree scale in 1742. His original scale was inverted — 0°C meant boiling, 100°C meant freezing — and was reversed by fellow Swede Carl Linnaeus shortly after his death.
Triple point of water – Frequently Asked Questions
What is the triple point of water?
The triple point of water is the unique combination of temperature and pressure (273.16 K / 0.01°C and 611.657 Pa) at which water can coexist as solid, liquid, and gas simultaneously. It is a fixed thermodynamic point that cannot vary — any change in temperature or pressure causes one phase to disappear.
Why was the triple point of water used to define the kelvin?
The triple point is a perfectly reproducible, invariant temperature — it occurs at exactly one pressure and temperature. From 1954 to 2019, the kelvin was defined as 1/273.16 of the thermodynamic temperature of the triple point of water, providing a stable international calibration reference accessible to any metrology lab.
What is the difference between the triple point and the freezing point of water?
The freezing point of water at standard atmospheric pressure is 273.15 K (0.00°C), while the triple point is 273.16 K (0.01°C) at 611.657 Pa. The triple point is 0.01°C warmer and occurs at much lower pressure than normal atmospheric conditions. Both are distinct and precisely defined reference points.
What replaced the triple point of water in the 2019 SI redefinition?
In the 2019 redefinition of SI units, the kelvin was redefined by fixing the value of the Boltzmann constant (k = 1.380649 × 10⁻²³ J/K) exactly. This makes the kelvin independent of any physical substance, more stable, and consistent with other SI redefinitions that fixed fundamental constants rather than relying on material artifacts.
Can the triple point of water occur naturally?
The triple point requires a pressure of about 611 Pa — roughly 0.6% of standard atmospheric pressure. On Earth's surface this does not occur naturally. On Mars, where atmospheric pressure is around 600–700 Pa at the surface, conditions near the triple point of water can occur, meaning liquid water, ice, and water vapor can briefly coexist on the Martian surface under the right conditions.
Celsius – Frequently Asked Questions
Which countries use Celsius?
Almost every country in the world uses Celsius for everyday temperatures — weather forecasts, cooking, and body temperature. The United States, Liberia, and Myanmar are the principal exceptions, using Fahrenheit for daily life, though US scientists use Celsius for research.
What is absolute zero in Celsius?
Absolute zero — the theoretical minimum temperature where molecular motion effectively ceases — is −273.15°C. This corresponds to 0 K on the kelvin scale. It is not physically achievable but has been approached to within a few billionths of a degree in laboratory conditions.
How do you convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 (or 1.8) and add 32. For example, 20°C × 1.8 + 32 = 68°F. A quick mental approximation: double the Celsius value and add 30 (gives ±2°F accuracy for typical weather temperatures).
What is normal body temperature in Celsius?
Normal human body temperature is approximately 37.0°C (98.6°F), though it varies by individual, time of day, and measurement site. A temperature above 38.0°C is generally considered a fever; hypothermia is diagnosed below 35.0°C.
What is the difference between Celsius and centigrade?
Centigrade is the old name for the same scale — both refer to a 100-degree span between water's freezing and boiling points ("centi" = 100, "grade" = step). The name was officially changed to Celsius in 1948 to avoid confusion with the angular unit also called "grade" (or "gradian") in some languages.