Why do different countries use different temperature scales?
General knowledgeAsked by Anonymous from Ashburn, United States24 Oct 2026, 1:04 AM ISTUpdated
In one line
Different countries use different temperature scales because they were invented in different places and times, and people got used to them.
Thermometer — Device to measure temperature A thermometer showing both Celsius and Fahrenheit scales, as often seen in India and the USA. Image: Wikipedia
The rule
Temperature scales are systems for measuring how hot or cold something is, using a set of fixed points and units.
The main scales are:
Celsius (°C): Used in most of the world.
Fahrenheit (°F): Used mainly in the United States.
Kelvin (K): Used in science everywhere.
Let's understand it simply
Imagine you and your friend both want to measure how hot your tea is. You use a steel ruler, your friend uses a plastic scale. Both give numbers, but they start and end at different points. Temperature scales are like these rulers. Each country started using the scale that was invented or popular there. People got used to it, so they kept using it.
Temperature Scales Compared
Celsius (°C)
Fahrenheit (°F)
Kelvin (K)
Freezing point of water
0°C
32°F
273 K
Boiling point of water
100°C
212°F
373 K
Used in
India, Europe, most countries
USA, some Caribbean countries
Science worldwide
How it works
Each scale picks two main points (like freezing and boiling of water).
The scale divides the space between these points into equal steps (degrees).
Celsius: Freezing is 0°C, boiling is 100°C.
Fahrenheit: Freezing is 32°F, boiling is 212°F.
Kelvin: Starts at absolute zero (the coldest possible), freezing is 273 K, boiling is 373 K.
The story behind it
Celsius was made by Anders Celsius in Sweden (1742). He wanted a simple scale for science. Fahrenheit was made by Daniel Fahrenheit in Germany (1724), using salt and ice for his zero point. Kelvin was made by Lord Kelvin in England (1848) for scientists who needed a scale starting at the coldest possible temperature.
History of Temperature Scales
1724Fahrenheit scale invented by Daniel Fahrenheit
1742Celsius scale invented by Anders Celsius
1848Kelvin scale introduced by Lord Kelvin
Where you see it in real life
Weather reports in India: Use Celsius ("Today is 35°C").
Weather in the USA: Uses Fahrenheit ("Today is 95°F").
Science labs: Use Kelvin ("Water boils at 373 K").
Cooking recipes: Ovens in the USA use Fahrenheit, in Europe use Celsius.
Air conditioner remotes: Often have a button to switch between °C and °F.
Why it matters
You need to know which scale is used, or you might get the wrong idea (35°C is hot, 35°F is cold!).
Science uses Kelvin for accuracy, so students and scientists must convert between scales.
International travel: You may see different scales in different countries.
Exams and higher studies often ask you to convert between scales.
Common mistakes
Mixing up the scales (thinking 100°F is boiling water — it's not!).
Forgetting to check which scale is being used in a question.
Using the wrong formula to convert between scales.
Remember it
Celsius for most of the world, Fahrenheit for the USA, Kelvin for science.
Check yourself
What is the freezing point of water in Celsius and Fahrenheit?
0°C in Celsius, 32°F in Fahrenheit.
Why do scientists use the Kelvin scale?
Because it starts at absolute zero, making calculations easier and more accurate.
If a weather report says it is 40°C, is that hot or cold? Why?
It is very hot, because Celsius is used in India and 40°C means a hot summer day.
Why do different countries stick to their own temperature scales?
Because people are used to them and changing would be confusing for daily life.
Quick recap
Different temperature scales were invented in different countries.
Celsius is used in most of the world, Fahrenheit mainly in the USA.
Kelvin is used in science everywhere.
Each scale sets its own zero and degree size.
Knowing the scale is important to avoid confusion.
