To convert Celsius to Fahrenheit, the exact formula is °F = (°C × 9/5) + 32. For a quicker mental calculation, you can use the approximation method: multiply the Celsius temperature by 2 and then add 30. This gives you a result within a few degrees of the exact conversion. For example, to convert 20°C: (20 × 2) + 30 = 70°F, which is close to the exact result of 68°F. This shortcut works reasonably well for temperatures in the normal environmental range. For more precise results, especially for scientific or medical purposes, use our converter tool above or the exact formula. Remember that the only temperature where Celsius and Fahrenheit are equal is -40 degrees.

The Celsius and Fahrenheit scales were developed by scientists in the 18th century using different approaches. The Celsius scale (originally called centigrade) was created by Swedish astronomer Anders Celsius in 1742. He initially defined 0° as the boiling point of water and 100° as the freezing point—the inverse of today’s scale. Shortly after his death, the scale was reversed to its current form. The Fahrenheit scale was developed by German physicist Daniel Gabriel Fahrenheit in 1724. He set 0°F based on the coldest temperature he could create with a mixture of ice, water, and ammonium chloride (a salt), while 96°F was based on human body temperature (later adjusted to 98.6°F). His scale set the boiling point of water at 212°F. The Celsius scale became widely adopted as part of the metric system, while Fahrenheit remained in use primarily in the United States and a few other countries.

Converting between Celsius and Fahrenheit is necessary because different regions of the world use different temperature scales. The United States primarily uses Fahrenheit for everyday measurements like weather forecasts, cooking, and body temperature, while most other countries use Celsius. This creates numerous situations requiring conversion: travelers need to understand weather forecasts in foreign countries; recipes from international cookbooks need temperature conversion for local ovens; scientists must often convert between scales when communicating research to the public; and imported appliances may use different temperature scales than what consumers are accustomed to. Additionally, in fields like medicine that operate globally, practitioners often need to convert between standards. As global communication and travel continue to increase, the ability to convert between Celsius and Fahrenheit remains an important practical skill despite efforts to standardize measurement systems internationally.

Neither Celsius nor Fahrenheit is inherently more accurate than the other—they’re simply different scales for measuring the same physical property. Both can be measured to arbitrary precision (e.g., 22.51°C or 72.518°F). However, Celsius has become the standard in scientific contexts worldwide for several practical reasons. First, it integrates seamlessly with the metric system. Second, it has more intuitive reference points: 0°C for water freezing and 100°C for water boiling at standard pressure. Third, the Kelvin scale (used in scientific calculations) is based on Celsius with the same degree size, just shifted to start at absolute zero (-273.15°C). In everyday use, some argue that Fahrenheit provides finer gradation without decimal places (0-100°F covers most temperatures humans regularly experience), while others prefer Celsius for its straightforward reference points. In terms of absolute accuracy, modern scientific temperature measurements typically use Celsius or Kelvin and can achieve precision to tiny fractions of a degree.

Celsius, Fahrenheit, and Kelvin are the three most common temperature scales, each with different reference points. The Celsius and Kelvin scales share the same degree size (a one-degree change in Celsius equals a one-degree change in Kelvin), but Kelvin starts at absolute zero (-273.15°C), the theoretical lowest possible temperature. To convert between them: K = °C + 273.15. The Fahrenheit scale uses a different degree size—a one-degree Celsius change equals a 1.8-degree Fahrenheit change. The conversion formulas are: °F = (°C × 9/5) + 32 and °C = (°F – 32) × 5/9. Key reference points across the scales: Water freezes at 0°C = 32°F = 273.15K; water boils at 100°C = 212°F = 373.15K; absolute zero is 0K = -273.15°C = -459.67°F; room temperature is approximately 20°C = 68°F = 293.15K; and normal human body temperature is about 37°C = 98.6°F = 310.15K. Scientists typically use Celsius or Kelvin, while Fahrenheit remains common for weather and body temperature in the United States.