Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, and Rankine temperature scales with our free temperature converter. Get accurate conversions instantly.
Calculate Your Temperature Converter
Formula: (°C × 9/5) + 32 = °F
0 °C = 32.00 °F
What is Temperature Conversion?
Temperature conversion is the process of changing a temperature from one unit of measurement to another. Different temperature scales are used around the world and in different contexts, making conversion necessary for international communication, science, cooking, and many other applications.
Common Temperature Scales
Celsius (°C)
- Used throughout most of the world for everyday temperature measurement
- In this scale, water freezes at 0°C and boils at 100°C at standard atmospheric pressure
- Originally called centigrade because it was based on a 100-degree scale
- The default temperature scale in scientific and medical contexts worldwide
Fahrenheit (°F)
- Primarily used in the United States for everyday temperature measurement
- In this scale, water freezes at 32°F and boils at 212°F at standard atmospheric pressure
- Developed by Daniel Gabriel Fahrenheit in the early 18th century
- Common reference points: 0°F (very cold winter day), 70°F (room temperature), 98.6°F (typical body temperature)
Kelvin (K)
- The base unit of temperature in the International System of Units (SI)
- Used primarily in scientific contexts, especially physics and chemistry
- Starts at absolute zero (0K), the theoretical temperature at which all molecular motion stops
- Has the same increment size as Celsius; water freezes at 273.15K and boils at 373.15K
- No degree symbol is used with Kelvin; write "300K" not "300°K"
Rankine (°R)
- Used primarily in engineering systems in the United States
- Like Kelvin, it starts at absolute zero (0°R)
- Uses the same increment size as Fahrenheit
- Water freezes at 491.67°R and boils at 671.67°R
How to Use the Temperature Converter
- Enter the temperature value you want to convert in the "Value" field
- Select the unit you're converting from in the "From" dropdown
- Select the unit you want to convert to in the "To" dropdown
- The result will automatically display in the "Result" field
- Use the swap button to quickly reverse the conversion direction
Common Conversion Formulas
| From | To | Formula |
|---|---|---|
| Celsius | Fahrenheit | °F = (°C × 9/5) + 32 |
| Fahrenheit | Celsius | °C = (°F − 32) × 5/9 |
| Celsius | Kelvin | K = °C + 273.15 |
| Kelvin | Celsius | °C = K − 273.15 |
| Fahrenheit | Kelvin | K = (°F − 32) × 5/9 + 273.15 |
| Kelvin | Rankine | °R = K × 9/5 |
Interesting Temperature Facts
- The Celsius and Fahrenheit scales are equal at -40 degrees (-40°C = -40°F)
- Body temperature is approximately 37°C (98.6°F)
- Absolute zero (0K or -273.15°C) is the lowest theoretically possible temperature
- The hottest temperature ever recorded on Earth was 56.7°C (134°F) in Death Valley, California, USA
- The coldest temperature ever recorded on Earth was -89.2°C (-128.6°F) at the Soviet Vostok Station in Antarctica
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Frequently Asked Questions
The use of different temperature scales is largely historical and cultural:
- Celsius was adopted by most countries during the metrication process in the 19th and 20th centuries as part of the standardized metric system.
- Fahrenheit remains in use in the United States due to historical precedent and the costs associated with changing established systems and practices.
- Kelvin is used universally in scientific contexts regardless of country, as it is the SI unit of temperature.
The persistence of multiple scales also reflects the significant effort and cost required to change established practices in industry, education, and daily life.
All temperature scales are equally accurate when properly used—they simply use different reference points and intervals. Kelvin is considered the standard scientific unit because it starts at absolute zero (the theoretical minimum temperature) and has fundamental significance in physics. For everyday use, the choice between Celsius and Fahrenheit is a matter of convenience and familiarity rather than accuracy. Scientists typically use Celsius or Kelvin for precision work, with Kelvin preferred for calculations involving thermodynamics.
Absolute zero (0 Kelvin, -273.15°C, or -459.67°F) is the theoretical temperature at which all molecular motion would stop. It represents the lowest possible temperature that could ever be achieved.
It's important because:
- It serves as a natural starting point for the Kelvin scale, which is essential in scientific calculations
- It helps scientists understand the fundamental behavior of matter
- It's a reference point for measuring thermal energy in a system
- Many physical properties like superconductivity emerge as temperatures approach absolute zero
While we can get extremely close to absolute zero in laboratories (within billionths of a degree), the laws of thermodynamics state that reaching exactly absolute zero is impossible.
Celsius and Fahrenheit scales meet at exactly -40 degrees. That means -40°C = -40°F. This happens because the two scales use different starting points and different interval sizes. The formula to convert between them is F = (C × 9/5) + 32. If you plug in -40 for C and solve the equation, you'll get -40 as the answer for F as well. This temperature is extremely cold—colder than the average winter temperatures in most inhabited places, but it can occur in polar regions and during severe cold snaps in northern countries.
Kelvin doesn't use the degree symbol (°) because it's an absolute temperature scale that wasn't defined relative to arbitrary reference points like the freezing and boiling points of water. Instead, it's defined based on absolute zero, a fundamental physical constant. In 1967, the 13th General Conference on Weights and Measures (CGPM) formally defined the unit as 'kelvin' rather than 'degree Kelvin' to emphasize this distinction. The correct notation is simply 'K' (e.g., '273.15 K' not '273.15°K'). This is similar to other SI base units like meter or second, which don't use special symbols.
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