BIPM-ratified constants · v1.0

Converter

Triple, point of water to kelvin converter calculator.

Convert triple point of water temperatures to Kelvin using T_K = T_°C + 273.15. Supports Celsius, Fahrenheit, and Rankine inputs.

From

celsius (°c) — triple point = 0.01 °c

celsius

0.01 celsius =273.16Kelvin

Equivalents

Precision: 6 dp · Notation: Decimal · 4 units

Celsius (°C) — triple point = 0.01 °Ccelsius273.16

Fahrenheit (°F) — triple point = 32.018 °Ffahrenheit255.3778

Rankine (°R) — triple point = 491.688 °Rrankine0.005556

Offset from triple point (°C)triple_point_offset_c273.17

Common pairings

1 celsiusequals255.9278 fahrenheit

1 celsiusequals0.555556 rankine

1 celsiusequals274.16 triple_point_offset_c

1 fahrenheitequals274.15 celsius

1 fahrenheitequals0.555556 rankine

1 fahrenheitequals274.16 triple_point_offset_c

1 rankineequals274.15 celsius

1 rankineequals255.9278 fahrenheit

The conversion

How the value
is computed.

Triple Point of Water to Kelvin Converter: Methodology and Formula

Understanding the Triple Point of Water

The triple point of water is the unique thermodynamic condition at which water coexists simultaneously as solid (ice), liquid, and vapor in thermodynamic equilibrium. This state occurs at precisely 0.01 degrees Celsius, 273.16 Kelvin, 32.018 degrees Fahrenheit, and 491.688 degrees Rankine, at a pressure of 611.657 Pascals (approximately 0.006 atm). Because this condition is perfectly reproducible in any laboratory worldwide, it serves as one of the most reliable fixed reference points in thermodynamic science and international metrology.

The Kelvin Scale and the Role of the Triple Point

The Kelvin (K) is the SI base unit of thermodynamic temperature, anchored so that absolute zero — the theoretical minimum at which all thermal motion ceases — equals exactly 0 K. Historically, the triple point of water played a defining role in establishing this scale. Prior to the 2019 SI redefinition, one kelvin was formally defined as exactly 1/273.16 of the thermodynamic temperature of the triple point of water, as documented by NIST SI Units — Temperature. This linkage made the triple point an indispensable calibration anchor for primary thermometry institutions worldwide.

The Conversion Formula

Converting any Celsius temperature to Kelvin follows a straightforward linear relationship:

T_K = T_°C + 273.15

The variables in this formula are:

T_K — Temperature expressed in Kelvin (K)
T_°C — Temperature expressed in degrees Celsius (°C)
273.15 — The fixed offset representing the difference between absolute zero (0 K) and the ice point of water (0 °C) at standard atmospheric pressure (101.325 kPa)

Applying this formula to the triple point of water yields: T_K = 0.01 + 273.15 = 273.16 K. This result matches the internationally accepted value, confirmed in The Kelvin and Temperature Measurements published by the National Institute of Standards and Technology (NIST). Note that the Celsius and Kelvin scales share an identical degree magnitude; only the zero reference point differs.

Converting From Fahrenheit and Rankine to Kelvin

When the input temperature is expressed in Fahrenheit or Rankine, apply the following intermediate steps before arriving at the Kelvin result:

From Fahrenheit (°F): T_K = (T_°F − 32) × 5/9 + 273.15. For the triple point: (32.018 − 32) × 5/9 + 273.15 = 0.01 + 273.15 = 273.16 K
From Rankine (°R): T_K = T_°R × 5/9. For the triple point: 491.688 × 5/9 = 273.16 K

All three starting scales converge on the same Kelvin output, verifying internal consistency across the conversion formulas.

Practical Applications in Science and Industry

The triple point of water in Kelvin carries significance far beyond academic thermodynamics:

Primary thermometry calibration: Standard platinum resistance thermometers (SPRTs) are calibrated at the triple point of water to achieve traceable, reproducible measurements in national metrology laboratories around the world.
Cryogenic research: Physicists working near absolute zero use the triple-point value as a high-confidence anchor when constructing low-temperature scales for superconductivity and quantum experiments.
Pharmaceutical and food safety: Precise temperature measurement — traceable to fixed thermodynamic points like the triple point — ensures vaccines, biologics, and perishables remain within validated storage ranges during cold-chain transport.
Atmospheric modeling: Climate and weather simulations depend on accurate phase-transition temperatures for water, and the triple-point value feeds directly into equations of state used in numerical weather prediction.

Worked Example

A laboratory technician measures a calibration cell at the triple point of water, reading 0.01 °C on a thermocouple. To report this value on the absolute Kelvin scale for a metrology publication, the technician applies: T_K = 0.01 + 273.15 = 273.16 K. This single value communicates the temperature without ambiguity, using an absolute reference that is consistent across all scientific disciplines and independent of historical ice-point conventions.

Sources

The conversion formula, triple-point values, and scale definitions referenced throughout this page are drawn from authoritative primary sources, including NIST SI Units — Temperature and The Kelvin and Temperature Measurements (NIST Journal of Research, Vol. 106). These represent the international consensus on thermodynamic temperature standards as maintained by national metrology institutes.

Reference

Frequently asked questions

What is the triple point of water in Kelvin?

The triple point of water equals exactly 273.16 Kelvin. This value is calculated by adding 273.15 to the Celsius triple-point temperature of 0.01 °C (T_K = 0.01 + 273.15 = 273.16 K). It marks the precise thermodynamic state at which water coexists as solid, liquid, and vapor simultaneously at a pressure of 611.657 Pascals, and has historically served as the primary defining fixed point for the international Kelvin temperature scale.

How do you convert the triple point of water from Celsius to Kelvin?

Use the formula T_K = T_°C + 273.15. Since the triple point of water is 0.01 °C, the conversion is: 0.01 + 273.15 = 273.16 K. This addition works because the Celsius and Kelvin scales share an identical degree magnitude — they differ only by a fixed offset of 273.15, which represents the interval between absolute zero (0 K) and the ice point of water (0 °C) at standard atmospheric pressure.

Why is the triple point of water used to define the Kelvin temperature scale?

The triple point of water is an ideal thermometric reference because it is perfectly reproducible: any pure water sample isolated at exactly 611.657 Pa will always reach 273.16 K at its triple point, regardless of where or when the measurement is made. Before the 2019 SI redefinition, one kelvin was formally set as 1/273.16 of this temperature, as documented by NIST. This reproducibility makes it far more reliable than reference points dependent on variable conditions such as atmospheric pressure or sample purity.

What is the difference between the triple point and the freezing point of water in Kelvin?

The freezing point of water at standard atmospheric pressure (101.325 kPa) is 273.15 K (0 °C), while the triple point is 273.16 K (0.01 °C) — a difference of exactly 0.01 K. This small gap arises because the triple point occurs at a much lower pressure of 611.657 Pa. At higher pressures, the liquid-solid equilibrium curve shifts, depressing the freezing temperature by approximately 0.01 degrees relative to the triple-point value.

How does the triple point of water in Kelvin relate to absolute zero?

Absolute zero, the coldest theoretically possible temperature at which all molecular thermal motion ceases, is defined as exactly 0 K (equivalent to −273.15 °C). The triple point of water at 273.16 K sits 273.16 degrees above absolute zero on the Kelvin scale. For an ideal gas, this means a system at the triple-point temperature holds 273.16 times more thermal energy per degree of freedom than a hypothetical system at absolute zero, highlighting the immense thermal span separating these two landmark temperatures.

Can this calculator convert the triple point temperature from Fahrenheit or Rankine to Kelvin?

Yes. The calculator accepts Celsius, Fahrenheit, and Rankine inputs. For Fahrenheit, it applies T_K = (T_°F − 32) × 5/9 + 273.15, converting the triple-point value of 32.018 °F to exactly 273.16 K. For Rankine, it uses T_K = T_°R × 5/9, converting 491.688 °R to 273.16 K. All three input scales produce the identical Kelvin output, confirming the mathematical consistency of the conversion formulas across temperature scales.