Temperature Converter
Convert temperature between Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur with accurate results, conversion formulas, common-unit comparisons, and step-by-step calculations.
Convert Temperature
Enter a temperature value, select the original temperature scale and the scale you want to convert to, then calculate the result.
Conversion Result
| Temperature Scale | Equivalent |
|---|---|
| Celsius | 0 °C |
| Fahrenheit | 32 °F |
| Kelvin | 273.15 K |
| Rankine | 491.67 °R |
| Réaumur | 0 °Ré |
Step-by-Step Calculation
What Is Temperature?
Temperature is a physical quantity used to describe how hot or cold something is. It is related to the average kinetic energy of particles in a substance and is measured using different temperature scales.
The most commonly encountered temperature scales are Celsius, Fahrenheit, and Kelvin. Rankine and Réaumur are also used in specific scientific, engineering, historical, or regional contexts.
How to Use the Temperature Converter
- Enter the temperature value you want to convert.
- Select the original temperature scale in the From dropdown.
- Select the desired temperature scale in the To dropdown.
- Click Convert Temperature.
- Review the converted result, common-scale table, formula, and step-by-step calculation.
Celsius (°C)
Celsius is one of the most widely used temperature scales. It is commonly used for weather, everyday temperatures, cooking, science, and many applications around the world.
Water freezes at 0 °C under standard atmospheric pressure
Water boils at 100 °C under standard atmospheric pressure
Celsius is also the basis for the Kelvin scale, with the Kelvin temperature obtained by adding 273.15 to the Celsius temperature.
Fahrenheit (°F)
Fahrenheit is widely used for everyday temperature measurements in the United States and is also encountered in some other regions and applications.
°F = (°C × 9/5) + 32
Fahrenheit to Celsius
°C = (°F − 32) × 5/9
Kelvin (K)
Kelvin is an absolute thermodynamic temperature scale and is the SI base unit for thermodynamic temperature.
K = °C + 273.15
°C = K − 273.15
Unlike Celsius, Kelvin does not use a degree symbol. For example, a temperature is written as 300 K rather than 300 °K.
Rankine (°R)
Rankine is an absolute temperature scale that uses the same size degree interval as Fahrenheit. It is primarily encountered in certain engineering and thermodynamic applications.
°R = (°C + 273.15) × 9/5
Rankine to Celsius
°C = (°R × 5/9) − 273.15
Réaumur (°Ré)
The Réaumur scale is a historical temperature scale. It is included here because it can still appear in historical references, specialized information, and older technical material.
°Ré = °C × 4/5
Réaumur to Celsius
°C = °Ré × 5/4
Temperature Conversion Formula Reference
Temperature conversion requires both scaling and offset adjustments. The calculator internally converts each input temperature to Celsius before converting it to the selected destination scale.
°F = (°C × 9/5) + 32
Fahrenheit → Celsius
°C = (°F − 32) × 5/9
Celsius → Kelvin
K = °C + 273.15
Kelvin → Celsius
°C = K − 273.15
Celsius → Rankine
°R = (°C + 273.15) × 9/5
Celsius → Réaumur
°Ré = °C × 4/5
Temperature Conversion Example
Example: Convert 25 °C to Fahrenheit.
Start with the Celsius-to-Fahrenheit formula:
°F = (°C × 9/5) + 32
°F = (25 × 9/5) + 32
°F = 45 + 32
25 °C = 77 °F
Common Temperature Reference Points
| Description | Approximate Temperature |
|---|---|
| Absolute zero | −273.15 °C / 0 K |
| Water freezing point | 0 °C / 32 °F / 273.15 K |
| Room temperature example | 20–25 °C / 68–77 °F |
| Water boiling point | 100 °C / 212 °F / 373.15 K |
Reference points involving water depend on pressure and conditions. The freezing and boiling values shown above use standard atmospheric pressure.
Can Temperature Be Negative?
Yes. Celsius and Fahrenheit temperatures can be below zero. Kelvin, however, begins at absolute zero and does not normally have negative values in ordinary thermodynamic temperature measurements.
0 K = −273.15 °C
0 K = −459.67 °F
Common Uses of Temperature Conversion
- Weather and climate information
- Cooking and food preparation
- Science and laboratory work
- Engineering and manufacturing
- Refrigeration and heating
- Industrial processes
- International temperature comparisons
- Thermodynamics and physics
What Happens If the Input Is Blank?
A blank numeric input is treated as zero. This allows the calculator to handle an empty field consistently.
For a meaningful conversion, enter the temperature value you want to convert before calculating.
Decimal Precision
The calculator performs internal temperature conversions using full numerical precision. Displayed calculated results are limited to a maximum of four decimal places for easier reading.
2.456789 → 2.4568
2.4567 → 2.4567
2.4500 → 2.45
Temperature Conversion vs. Temperature Difference
Converting a temperature reading is different from converting a temperature change. For example, a 10 °C temperature difference has the same size interval as 10 K, but a temperature reading of 10 °C is not equal to 10 K because the scales have different zero points.
For ordinary conversions between temperature readings, the calculator applies the appropriate offset and scale factor. This is why Celsius and Fahrenheit require both multiplication and addition or subtraction.
Why Kelvin Is Different
Kelvin is an absolute thermodynamic temperature scale. Its zero point is absolute zero, while Celsius uses a shifted zero point. The interval size between Celsius and Kelvin is identical, so a change of 1 °C corresponds to a change of 1 K.
This makes Kelvin especially useful in physics, chemistry, thermodynamics, and scientific equations where absolute temperature is required.
Common Temperature Conversion Mistakes
- Forgetting the 32-degree offset when converting between Celsius and Fahrenheit.
- Writing Kelvin with a degree symbol; the correct notation is K.
- Treating a temperature reading and a temperature difference as if they were the same type of quantity.
- Using water’s freezing or boiling point without considering pressure.
- Rounding intermediate calculations unnecessarily before the final result.
Choosing the Right Temperature Scale
Use Celsius for most everyday measurements in countries that use the metric system, Fahrenheit where that scale is customary, and Kelvin when an absolute thermodynamic temperature is required. Rankine can appear in engineering and thermodynamic work, while Réaumur is mainly encountered in historical or specialized references.
Frequently Asked Questions
What is a temperature converter?
A temperature converter changes a temperature measurement from one temperature scale to another, such as Celsius to Fahrenheit or Fahrenheit to Celsius.
What is the formula for Celsius to Fahrenheit?
The formula is °F = (°C × 9/5) + 32.
What is 0 °C in Fahrenheit?
0 °C equals 32 °F.
What is 100 °C in Fahrenheit?
100 °C equals 212 °F.
What is 25 °C in Fahrenheit?
25 °C equals 77 °F.
What is the difference between Celsius and Kelvin?
Celsius and Kelvin have the same size temperature interval, but their zero points differ by 273.15. Therefore, K = °C + 273.15.
Can Kelvin be negative?
Ordinary thermodynamic temperatures are expressed on the Kelvin scale starting from absolute zero, so standard Kelvin temperatures are not negative.
What is absolute zero?
Absolute zero is 0 K, equivalent to −273.15 °C and −459.67 °F.
What is the Réaumur scale?
Réaumur is a historical temperature scale in which the interval between the freezing and boiling points of water was divided into 80 degrees under its traditional reference conditions.
What is the Rankine scale?
Rankine is an absolute temperature scale using the same degree size as Fahrenheit.
What happens if the temperature input is blank?
A blank input is treated as zero.
Temperature Converter Disclaimer
This calculator is provided for general educational, informational, and estimation purposes only. Conversion results are based on standard mathematical relationships between temperature scales and the values entered by the user. Reference points involving water may depend on pressure and other conditions. For scientific, laboratory, medical, industrial, engineering, safety-critical, regulatory, or other high-precision applications, results should be independently verified using applicable standards, calibrated instruments, environmental conditions, and qualified expertise.