SpecCalcsReference calculators for the shop floor

Temperature Converter

100 °C (water's boiling point at 1 atm) is 212 °F, 373.15 K, and 671.67 °R — enter any temperature below to convert across all four scales.

Enter a temperature and select the source scale
Celsius100
Fahrenheit212
Kelvin373.15
Rankine671.67

Conversion formulas

Celsius ↔ Fahrenheit
TF=TC×95+32T_F = T_C \times \tfrac{9}{5} + 32
Celsius ↔ Kelvin
TK=TC+273.15T_K = T_C + 273.15
Fahrenheit ↔ Rankine
TR=TF+459.67T_R = T_F + 459.67
273.15 and 459.67 are exact offsets, not approximations

Celsius and Kelvin share the same degree size — a 1 °C change equals a 1 K change — but their zeros differ by exactly 273.15. Fahrenheit and Rankine share the same degree size too, offset by 459.67. The ⅔ ratio between the two degree sizes (9/5) is exact by definition, not a measurement.

Absolute zero

Absolute zero is 0 K = −273.15 °C = −459.67 °F = 0 °R. It is the lowest temperature permitted by thermodynamics — the point at which a system has minimum possible energy. Kelvin and Rankine are absolute scales (their zero is absolute zero); Celsius and Fahrenheit are relative scales with arbitrary zero points (water's freezing point and the lowest temperature Fahrenheit could create with a salt-ice mixture, respectively).

When each scale is used

Celsius is the worldwide standard for everyday, scientific, and engineering temperatures. Fahrenheit is used in the United States for weather, cooking, and body temperature. Kelvin is the SI unit — required in thermodynamics, gas-law calculations, and anywhere a ratio of temperatures is meaningful (you cannot take a ratio in Celsius because 0 °C is not zero energy). Rankine serves the same absolute-scale role for Fahrenheit-based engineering, appearing in US-customary thermodynamic tables and some HVAC calculations.