Centigrade and Celsius: A Brief History
In 1742, Swedish astronomer Anders Celsius introduced a temperature scale with 100 equal divisions between the freezing and boiling points of water—the origin of the term 'centigrade' (Latin for 'hundred steps'). Initially, the scale was inverted, with 0° at boiling and 100° at freezing. By 1743, physicist Jean-Pierre Christin reversed it to match modern convention.
The formal name changed to the Celsius scale in 1948 as a tribute to Anders Celsius. However, 'centigrade' remained in common use for decades, particularly in older scientific texts and some countries. Today, both terms identify the identical temperature scale—there is no mathematical difference between them.
The Centigrade–Celsius Conversion
Converting between centigrade and Celsius requires no calculation: they are one and the same unit. Any temperature expressed in centigrade equals that exact value in Celsius.
°Celsius = °Centigrade
°Centigrade— Temperature measured on the centigrade scale°Celsius— Temperature measured on the Celsius scale (numerically identical)
Using the Converter
Enter a temperature value in either field to see its equivalent instantly:
- From centigrade: Input your temperature (for example, 25°C) in the first field. The result displays immediately in the second field, also as 25°C.
- Reverse conversion: You can equally enter a Celsius value and retrieve the centigrade equivalent with no change to the number.
- Negative temperatures: The converter handles sub-zero values without modification. For instance, −40° centigrade equals −40° Celsius.
Key Points to Remember
Understanding these distinctions will help you work confidently with both temperature scales.
- Nomenclature vs. scale — The shift from 'centigrade' to 'Celsius' was a naming convention change in 1948, not a redefinition of the scale itself. If you encounter old documents labelled centigrade, the numerical values are directly comparable to modern Celsius measurements.
- Regional language differences — Many non-English-speaking countries continued using 'centigrade' in everyday speech and education long after 1948. In some contexts, you may see the older term in scientific or engineering literature, but the underlying scale remains unchanged.
- Precision with real-world data — While the conversion is straightforward, always verify temperature data sources and measurement conditions. Water freezes at 0° in both scales under standard atmospheric pressure, but anomalous conditions can shift these reference points slightly.
- Beyond Celsius: other scales — When converting to Kelvin (absolute temperature) or Fahrenheit, you must apply proper formulas. Centigrade–Celsius equivalence is unique; don't assume the same 1:1 relationship exists with other temperature units.
Temperature Reference Points
Several key temperatures anchor both scales:
- Water freezes: 0° Celsius (0° centigrade)
- Water boils: 100° Celsius (100° centigrade) at standard atmospheric pressure
- Absolute zero: −273.15° Celsius, the theoretical lowest possible temperature where all molecular motion ceases
- Room temperature: Typically 20–25° Celsius (same in centigrade)
These reference points are identical for both scales because they describe the same physical phenomena.