What is Temperature?

Temperature is a physical quantity that expresses the degree of hotness or coldness of a substance. It is a measure of the average kinetic energy of the particles in an object, which is the energy of their motion. The higher the temperature, the faster the particles are moving. To measure this property, we use standardized scales, the most common of which are Celsius, Fahrenheit, and Kelvin.

The Celsius Scale (°C)

The Celsius scale, part of the metric system, is the most widely used temperature scale in the world for everyday purposes. It was developed by Swedish astronomer Anders Celsius in 1742. The scale is based on two fundamental points:

• 0°C: The freezing point of water at standard atmospheric pressure.
• 100°C: The boiling point of water at standard atmospheric pressure.

The interval between these two points is divided into 100 equal degrees, making it a simple and intuitive centigrade scale.

The Fahrenheit Scale (°F)

The Fahrenheit scale was proposed by physicist Daniel Gabriel Fahrenheit in 1724. It is primarily used in the United States and a few other countries. Its reference points are different:

• 32°F: The freezing point of water.
• 212°F: The boiling point of water.

The 180-degree interval between these points makes for smaller degree increments than the Celsius scale, which some argue allows for more precision in describing everyday temperatures without using decimals.

The Kelvin Scale (K): The Absolute Scale

The Kelvin scale is the base unit of thermodynamic temperature in the International System of Units (SI). It is an absolute scale, meaning its zero point, 0 K, is "absolute zero"—the theoretical point at which all molecular motion ceases. There are no negative numbers on the Kelvin scale. The size of one Kelvin is the same as one degree Celsius. Because of its absolute nature, Kelvin is the standard scale used in scientific and engineering fields.

• 0 K: Absolute zero (-273.15 °C)
• 273.15 K: The freezing point of water.
• 373.15 K: The boiling point of water.

Conversion Formulas

Converting between these scales requires specific mathematical formulas because their zero points are different.

Celsius to Fahrenheit:

°F = (°C × 9/5) + 32

Fahrenheit to Celsius:

°C = (°F - 32) × 5/9

Celsius to Kelvin:

K = °C + 273.15

Frequently Asked Questions (FAQs)

1. How do I use the Temperature Converter?

Simply type a value into any of the three input boxes (Celsius, Fahrenheit, or Kelvin). The other two boxes will automatically update with the converted values in real-time. The animated thermometer will also adjust to visualize the temperature.

2. Why does the calculator handle three inputs at once?

This bidirectional design allows for maximum flexibility. You can start with whichever unit you know and instantly see its equivalent in the other two systems without needing to select any options from a dropdown menu.

3. Is there a temperature at which Celsius and Fahrenheit are equal?

Yes. -40°C is equal to -40°F. It is the only point at which the two scales intersect.