Celsius — Definition, Formula & Examples
Celsius is a unit for measuring temperature. On the Celsius scale, water freezes at 0 degrees and boils at 100 degrees.
The Celsius scale (°C) is a metric temperature scale defined by two fixed reference points: 0 °C at the freezing point of pure water and 100 °C at its boiling point, both at standard atmospheric pressure, with the interval divided into 100 equal parts.
Key Formula
Where:
- = Temperature in degrees Fahrenheit
- = Temperature in degrees Celsius
How It Works
Celsius temperatures tell you how hot or cold something is compared to the freezing and boiling points of water. Readings below 0 °C are below freezing and use negative numbers. To convert a Celsius temperature to Fahrenheit, multiply by 9/5 and then add 32. To go from Fahrenheit to Celsius, subtract 32 and then multiply by 5/9.
Worked Example
Problem: A thermometer reads 25 °C. What is that temperature in Fahrenheit?
Step 1: Multiply the Celsius temperature by 9/5.
Step 2: Add 32 to the result.
Answer: 25 °C equals 77 °F.
Why It Matters
Celsius is used in science classes and in most countries around the world for weather, cooking, and lab experiments. Learning to read and convert Celsius temperatures helps you understand data in science projects, word problems, and real-life travel situations.
Common Mistakes
Mistake: Forgetting to add 32 when converting Celsius to Fahrenheit, giving an answer that is 32 degrees too low.
Correction: Always complete both steps of the formula: first multiply by 9/5, then add 32.