Science & everyday life
Celsius vs Fahrenheit
Both scales measure temperature. They use different reference points and different-sized degrees—so the same weather feels like a different number depending on which scale you use.
What is Celsius?
Celsius (°C) is used in most of the world. Water freezes at 0°C and boils at 100°C at normal air pressure. Room temperature is roughly 20–22°C; a hot summer day might be 30°C or more.
The scale is named after Anders Celsius. It fits neatly with the metric system, which is why scientists and international weather reports usually prefer it.
What is Fahrenheit?
Fahrenheit (°F) is common in the United States and a few other places. On this scale, water freezes around 32°F and boils around 212°F. Comfortable indoor heat is often about 68–72°F.
Daniel Gabriel Fahrenheit designed the scale in the early 1700s. Each degree Fahrenheit is smaller than a degree Celsius, so the numbers change more quickly for the same change in heat.
Celsius (°C)
0 = freezing water
100 = boiling water
Used widely worldwide
Fahrenheit (°F)
32 = freezing water
212 = boiling water
Common in the U.S.
Quick conversion
You do not need to memorize both scales. These formulas convert in either direction:
°C = (°F − 32) × 5/9
Example: 25°C is (25 × 9/5) + 32 = 77°F. 98.6°F (a classic “body temperature” figure) is about 37°C.
Same day, different numbers
| Situation | Celsius | Fahrenheit |
|---|---|---|
| Very cold winter | −10°C | 14°F |
| Cool spring morning | 10°C | 50°F |
| Pleasant room | 21°C | 70°F |
| Hot summer afternoon | 35°C | 95°F |
Which should you use?
Use whatever your audience expects: Celsius for most international readers and science; Fahrenheit where local custom still favors it. The physical temperature is the same—only the label on the number changes.
A riddle
Two systems describe the same world, yet their numbers rarely agree.
In one, ice is zero and boiling is one hundred. In the other, ice is thirty-two and boiling
is two hundred twelve. A comfortable room is twenty-one in the first and seventy in the second;
a hot day might read thirty-five or ninety-five for the same air.
You can multiply by nine, divide by five, add or subtract thirty-two—you only change the label,
not the reality.
I am not Celsius. I am not Fahrenheit. I am not a scale, not a digit, not the glass tube.
What am I called?
Hint: Both scales measure the same property of the air in the room. Converting °C to °F does not change that property.
Correct: temperature. Celsius and Fahrenheit are different ways to express the same thing.