Temperature Converter

What is Temperature?

Temperature is a physical quantity that expresses the degree of hotness or coldness of a substance or environment. At the microscopic level, temperature reflects the average kinetic energy of the particles (atoms and molecules) in a material. When particles move faster, the temperature is higher; when they move slower, the temperature is lower. This fundamental property of matter affects everything from weather patterns and chemical reactions to cooking times and engine performance.

Unlike length or mass, temperature is an intensive property, meaning it does not depend on the amount of matter present. A cup of boiling water and a pot of boiling water have the same temperature, even though the pot contains much more water and therefore more total thermal energy. Understanding temperature and how to convert between different scales is essential in science, engineering, medicine, cooking, and everyday life.

Throughout history, humans have developed several different scales to measure temperature, each with its own reference points and units. The three most widely used scales today are Celsius, Fahrenheit, and Kelvin, and our converter makes it easy to switch between them instantly.

Temperature Scales Explained

Celsius (°C)

The Celsius scale, also known as the centigrade scale, is the most widely used temperature scale in the world. It was developed by Swedish astronomer Anders Celsius in 1742. The scale defines 0°C as the freezing point of water and 100°C as the boiling point of water at standard atmospheric pressure. Celsius is used in virtually every country except the United States and a few territories, and it is the standard scale for scientific work in most fields. Weather forecasts, medical thermometers, cooking instructions, and classroom experiments around the world all use Celsius.

Fahrenheit (°F)

The Fahrenheit scale was created by German physicist Daniel Gabriel Fahrenheit in 1724. It sets 32°F as the freezing point of water and 212°F as the boiling point, placing 180 degrees between the two. The Fahrenheit scale is primarily used in the United States, its territories, and a handful of other nations. It is commonly seen in weather reports, oven temperatures, body temperature readings, and automotive thermostats in these regions. Many Americans find Fahrenheit more intuitive for everyday weather because the scale provides finer granularity in the temperature range most people experience.

Kelvin (K)

The Kelvin scale is the base unit of temperature in the International System of Units (SI). Named after the British physicist Lord Kelvin, it starts at absolute zero, the theoretical point where all atomic motion ceases. Unlike Celsius and Fahrenheit, Kelvin does not use the degree symbol; temperatures are simply written as, for example, 300 K. The Kelvin scale is essential in physics, chemistry, astronomy, and engineering because many scientific laws and formulas require temperatures expressed on an absolute scale. A change of one Kelvin is exactly equal to a change of one degree Celsius, making conversions between the two straightforward.

Conversion Formulas

Converting between temperature scales requires specific formulas because each scale has different zero points and different step sizes. Here are the key formulas:

• Celsius to Fahrenheit:°F = (°C × 9/5) + 32
• Fahrenheit to Celsius:°C = (°F − 32) × 5/9
• Celsius to Kelvin:K = °C + 273.15
• Kelvin to Celsius:°C = K − 273.15
• Fahrenheit to Kelvin:K = (°F − 32) × 5/9 + 273.15
• Kelvin to Fahrenheit:°F = (K − 273.15) × 9/5 + 32

Notice that converting between Celsius and Kelvin is simply a matter of adding or subtracting 273.15, because the two scales have the same step size. Converting to or from Fahrenheit requires both multiplication and addition because the Fahrenheit scale has a different step size (a Fahrenheit degree is 5/9 the size of a Celsius degree) and a different zero point.

How to Use This Tool

Our Temperature Converter allows you to convert between Celsius, Fahrenheit, and Kelvin in real time. Simply type a number into any of the three input fields, and the other two fields will update automatically with the converted values. There is no need to press a button or wait for the result.

You can also click any row in the reference points table below the input fields to instantly load a common temperature such as the freezing point of water, body temperature, or the boiling point of water. Each input field also has a copy button so you can quickly grab the converted value for use in documents, spreadsheets, or code. All calculations are performed entirely in your browser, so your data stays private.

Frequently Asked Questions

What is absolute zero?

Absolute zero is the lowest possible temperature, defined as 0 K (−273.15°C or −459.67°F). At this temperature, the thermal motion of particles theoretically ceases entirely. While scientists have come extremely close to reaching absolute zero in laboratory settings, it is impossible to reach it in practice according to the third law of thermodynamics.

Why does the United States use Fahrenheit?

The United States adopted the Fahrenheit scale in the 18th century and has retained it ever since, despite the rest of the world switching to Celsius. Efforts to metricate the US during the 1970s met with limited public acceptance, and Fahrenheit remains deeply ingrained in American culture, weather reporting, cooking, and industry.

Can negative temperatures exist in Kelvin?

In the standard Kelvin scale, negative temperatures do not exist because 0 K is defined as absolute zero, the lowest possible temperature. However, in certain specialized physics contexts involving quantum systems with inverted populations, scientists sometimes describe so-called negative absolute temperatures, which are actually hotter than any positive temperature. These are not relevant to everyday temperature measurement.

How accurate is this converter?

This converter displays results to four decimal places, which is sufficient for virtually all practical purposes. The underlying conversion formulas are mathematically exact. For extremely precise scientific work requiring more significant figures, you may want to use specialized software, but for cooking, weather, travel, and general science, this tool provides more than enough precision.