Fahrenheit vs Celsius: Understanding Temperature Scales
A clear explanation of both temperature scales, how to convert between them, and why the world uses two different systems.
Use the Fahrenheit ↔ Celsius
Convert between °F and °C
Two Scales, One Phenomenon
Both Fahrenheit and Celsius measure the same physical property, temperature, but they use completely different reference points to define their scales. Anders Celsius, a Swedish astronomer, designed his scale around the behavior of water: 0 degrees is where water freezes and 100 degrees is where it boils at standard atmospheric pressure. This gives the scale a clean, intuitive structure. Daniel Gabriel Fahrenheit, a German physicist, based his scale on different references: 0 degrees was the temperature of a brine solution (a mixture of ice, water, and ammonium chloride), and he set human body temperature at 96 degrees, which was later corrected to 98.6 degrees as measurement instruments improved.
The Conversion Formulas
To convert Celsius to Fahrenheit, multiply the Celsius temperature by 9, divide by 5, and add 32. In formula form: F = (C x 9/5) + 32. To go the other direction, subtract 32 from the Fahrenheit temperature, then multiply by 5/9. So C = (F - 32) x 5/9.
Key Temperatures to Memorize
Having a few reference points memorized makes it much easier to think in either scale.
Which Countries Use Which
The vast majority of the world uses Celsius for everyday temperature measurement. Only the United States, the Bahamas, Palau, the Cayman Islands, and a handful of US territories use Fahrenheit as their primary scale. Scientists everywhere use Celsius or Kelvin regardless of what country they are in. Weather forecasts in Europe, Asia, Africa, South America, and Australia are all given in Celsius. This means that if you travel internationally or follow weather reports from other countries, understanding both scales is genuinely useful, not just academic.
Why Fahrenheit Persists in the US
The United States came close to switching to the metric system in the 1970s when Congress passed the Metric Conversion Act of 1975. However, the law made conversion voluntary rather than mandatory, and public enthusiasm faded quickly. Fahrenheit remains deeply embedded in American culture, from cooking recipes and thermostat settings to weather forecasts and fever thresholds. Most Americans instinctively know that 72 degrees is comfortable and 100 degrees is dangerously hot, but would need to think carefully about what 22 degrees Celsius or 38 degrees Celsius feel like. Changing an entire country's everyday habits is a massive undertaking, and without a strong mandate, the switch has never gained enough momentum.