Centigrade, now more commonly known as Celsius, and Fahrenheit are two temperature scales used around the world. While Celsius is the standard in most countries for everyday temperature measurements and scientific applications, Fahrenheit is still primarily used in the United States. Understanding the differences between these scales, their origins, and how to convert between them is essential for anyone dealing with temperature measurements. This article will delve into a detailed comparison of Centigrade (Celsius) and Fahrenheit, exploring their definitions, history, usage, and conversion methods.
What are Celsius and Fahrenheit?
Both Celsius and Fahrenheit are thermometric scales, meaning they are used to measure temperature. However, they differ significantly in their reference points and the size of their degrees.
Celsius (Centigrade) Explained
The Celsius scale, originally called centigrade, is part of the metric system and is based on the properties of water. It was devised by Swedish astronomer Anders Celsius in the 18th century. The scale defines the freezing point of water at 0 degrees Celsius (°C) and the boiling point of water at 100 degrees Celsius at standard atmospheric pressure. The term “centigrade” refers to the 100-degree interval between these two points. Although officially renamed Celsius in 1948 by the Ninth General Conference on Weights and Measures, the term “centigrade” is still sometimes used, especially in older contexts or certain regions.
Fahrenheit Explained
The Fahrenheit scale is named after German physicist Daniel Gabriel Fahrenheit, who developed it in the early 18th century. Fahrenheit initially defined his scale using a mixture of ice, water, and salt for 0 degrees, and the temperature of the human body for around 96 degrees. He later refined it to use the freezing point of water at 32 degrees Fahrenheit (°F) and the boiling point of water at 212 degrees Fahrenheit. This system places the boiling and freezing points of water exactly 180 degrees apart.
Key Differences Between Celsius and Fahrenheit
While both scales measure temperature, several key differences set them apart:
Origin and Definition
- Celsius: Based on the metric system and defined by the freezing (0°C) and boiling (100°C) points of water. It is now more precisely defined by absolute zero and the triple point of water for scientific accuracy, but for practical purposes, the water points remain the fundamental definition.
- Fahrenheit: Historically based on a brine mixture and human body temperature, later redefined by the freezing (32°F) and boiling (212°F) points of water.
Freezing and Boiling Points of Water
- Celsius: Freezing point of water is 0°C, boiling point is 100°C.
- Fahrenheit: Freezing point of water is 32°F, boiling point is 212°F.
Degree Size
The size of one degree differs between the two scales. A change of one degree Celsius is larger than a change of one degree Fahrenheit.
- Relationship: One degree Celsius is equal to 1.8 degrees Fahrenheit. Conversely, one degree Fahrenheit is equal to 5/9 (or approximately 0.556) of a degree Celsius. This difference in degree size arises from the different intervals between the freezing and boiling points of water on each scale (100 degrees for Celsius vs. 180 degrees for Fahrenheit).
Common Usage
- Celsius: Used in most countries worldwide for everyday temperature reporting, weather forecasts, and scientific applications. It is the standard scale in the metric system.
- Fahrenheit: Primarily used in the United States, its territories, and a few other countries for non-scientific purposes, such as weather reporting and household thermometers. Some older generations in English-speaking countries might still use Fahrenheit, especially for air temperature.
Conversion Formulas
Converting between Celsius and Fahrenheit is straightforward using these formulas:
Celsius to Fahrenheit:
°F = (°C × 9/5) + 32
Fahrenheit to Celsius:
°C = (°F – 32) × 5/9
For example, to convert 25°C to Fahrenheit:
°F = (25 × 9/5) + 32 = (45) + 32 = 77°F
To convert 68°F to Celsius:
°C = (68 – 32) × 5/9 = (36) × 5/9 = 20°C
It’s also notable that -40 degrees is the point where both scales coincide: -40°C is equal to -40°F.
History of Celsius and Fahrenheit Scales
Both scales have historical roots tied to the development of thermometry and the need for standardized temperature measurement.
Fahrenheit Scale History: Developed by Daniel Gabriel Fahrenheit, the scale gained early adoption in the Netherlands and parts of Scandinavia. Its use spread within the British Empire and became common in English-speaking countries.
Celsius Scale History: Anders Celsius originally defined his scale in reverse, with 0°C as the boiling point and 100°C as the freezing point of water. This was later inverted to the current standard. The Celsius scale became increasingly adopted as part of the metric system’s global expansion, particularly in scientific communities due to its decimal-based nature and direct relation to water’s properties. The move toward metrication in many countries during the mid to late 20th century further cemented Celsius as the dominant scale worldwide.
Why Two Scales?
The persistence of two major temperature scales often leads to questions about their relative advantages. Arguments have been made for the “user-friendliness” of Fahrenheit, suggesting that smaller degree increments allow for more precise communication of temperature differences without fractions. Furthermore, the typical range of ambient air temperatures in many inhabited regions falls roughly between 0°F and 100°F, making this scale seem intuitively aligned with everyday temperature experiences for those accustomed to it.
However, Celsius is often favored for its simplicity and direct correlation to a fundamental substance, water. The 0-100 range is easy to grasp and remember, and its integration with the metric system provides consistency across various scientific and engineering disciplines. Categorizations like 0-10°C (cold), 10-20°C (mild), 20-30°C (warm), and 30-40°C (hot) demonstrate that Celsius can also be intuitively understood in daily life.
Ultimately, the widespread use of Celsius is largely due to its adoption as the international standard within the metric system, while Fahrenheit’s continued use is mainly concentrated in specific regions due to historical and cultural reasons.
Conclusion
Understanding the difference between Centigrade (Celsius) and Fahrenheit is crucial in a globalized world. While Celsius has become the international standard for most applications, Fahrenheit remains relevant in certain regions, particularly the United States. Knowing the key differences in their definitions, degree sizes, and conversion formulas allows for effective communication and accurate temperature interpretation regardless of the scale used. Both scales serve the purpose of measuring temperature, but their historical development and standardization paths have led to the dual system we observe today.
Celsius and Fahrenheit thermometers side by side compare the two scales. The freezing point of water is 0 Celsius or 32 degrees Fahrenheit. The boiling point of water is 100 Celsius or 212 degrees Fahrenheit.
References
- Diffen.com. “Celsius vs Fahrenheit.” Diffen.com. Diffen LLC, n.d. Web. 27 Jan 2025. < >
- International Bureau of Weights and Measures (BIPM)
- National Institute of Standards and Technology (NIST)
- Wikipedia articles on Celsius and Fahrenheit scales
