Fahrenheit to Celsius formula
°C = (°F − 32) × 5⁄9 Example: (68°F − 32) × 5⁄9 = 36 × 5⁄9 = 20°C The simple mental math shortcut
To quickly estimate the temperature in your head without a calculator, use this inverted trick: Subtract 30 from the Fahrenheit temperature, then cut the number in half. While this provides a rough estimate rather than a precise decimal, it's perfect for quick weather checks. For example, if it is 70°F outside: 70 minus 30 is 40, and half of that is 20°C (the exact answer is 21.11°C).
About the Fahrenheit scale
Invented in 1724 by the physicist Daniel Gabriel Fahrenheit, this scale was the world's first standardized temperature system to achieve widespread adoption. It establishes the freezing point of pure water at exactly 32°F and its boiling point at 212°F under standard atmospheric pressure. This creates a neat 180-degree grid between freezing and boiling. Today, the Fahrenheit scale is used primarily within the United States and its territories for everyday weather and commerce.
About the Celsius scale
The Celsius scale (traditionally known as centigrade) is a core component of the international metric system used globally. Originally proposed by Swedish astronomer Anders Celsius in 1742, its design is elegantly straightforward: 0°C represents the freezing point of water, and 100°C represents the boiling point at sea level. Because it divides the states of water into a perfect 100-step scale, it remains the universal standard for science and international metrics.
Reference table
| Fahrenheit | Celsius |
|---|---|
| −40°F | −40°C (the crossing point) |
| 32°F | 0°C (freezing) |
| 68°F | 20°C (room temperature) |
| 98.6°F | 37°C (body temperature) |
| 212°F | 100°C (boiling) |
Frequently asked questions
What is 98.6°F in Celsius?
98.6°F is 37°C, the traditional reference for normal human body temperature. Subtract 32, then multiply by 5⁄9 (about 0.556): (98.6 − 32) × 0.556 = 37.
How do I convert an oven temperature from Fahrenheit to Celsius?
Use the same formula: subtract 32, then multiply by 5⁄9. A 350°F oven is about 177°C. Many recipes round to the nearest 5 or 10 degrees since home ovens rarely hold the exact number anyway.
Why does the US use Fahrenheit while most of the world uses Celsius?
Fahrenheit was the standard across the British Empire until most countries metricated in the mid-20th century; the US did not follow. Celsius ties neatly to water's freezing and boiling points (0° and 100°), which is why it dominates science and most of the world today.
Need the reverse direction? See Celsius to Fahrenheit.