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Temperature Conversion
About This Tool
Temperature Conversion is an online temperature unit conversion tool that supports mutual conversion among five temperature units: Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), and Réaumur (°Ré). Enter any value and unit to instantly see the corresponding results in all other units—ideal for daily life, scientific research, cooking, and international travel.
How to Use
- Enter a value
Input the temperature value to convert in the field, supporting integers and decimals such as
100,36.5,-40 - Select source unit
Choose the unit of the current value from the dropdown (°C/°F/K/°R/°Ré)
- View results
Click the "Convert" button or press Enter—the result area below will display the corresponding values in all temperature units, each with a copy button for easy use
Use Cases
- International travel: The United States uses Fahrenheit (°F) while China and most other countries use Celsius (°C). Quickly convert Fahrenheit to Celsius when checking local weather forecasts abroad, e.g., 86°F ≈ 30°C
- Scientific research: Physics, chemistry, and engineering commonly use Kelvin (K) as the absolute temperature scale, where 0 K is absolute zero. Convert experimental data between Celsius and Kelvin for thermodynamic calculations
- Cooking and baking: Oven temperatures in international recipes are often listed in Fahrenheit, e.g., 350°F ≈ 176.7°C. Use this tool to quickly convert to familiar Celsius for precise baking temperature control
Core Advantages
- Daily Free Quota
We provide free usage every day, so light everyday needs can be met at zero cost — no payment required to complete temperature conversions.
- No Install or Sign-up
Open the web page and use it directly — no software to download, install, or account registration required.
- Privacy & Security
All conversions are performed locally in your browser, and your input data is never uploaded to any server, protecting your privacy 100%.
- All Units at Once
Enter a single value to instantly see the corresponding results in °C, °F, K, °R, and °Ré — no need to convert one by one.
- Easy Copying
Each result has a copy button on its right; click it to copy the value and paste it into documents, reports, or spreadsheets.
- Instant Response
Results appear instantly when you input a value or switch units, making it ideal for batch queries, engineering calculations, and teaching demonstrations.
Temperature Unit Conversion Formulas
The following are the conversion formulas among the five common temperature units, using Celsius (°C) as the reference:
| Unit Name | Symbol | Formula (from °C) |
|---|---|---|
| Celsius | °C | °C = K - 273.15 |
| Fahrenheit | °F | °F = (°C × 9/5) + 32 |
| Kelvin | K | K = °C + 273.15 |
| Rankine | °R | °R = (°C + 273.15) × 9/5 |
| Réaumur | °Ré | °Ré = °C × 4/5 |
Common Temperature Reference Values
Below are common temperature values in daily life, covering the three most frequently used temperature units (°C, °F, K):
| Reference Point | °C | °F | K |
|---|---|---|---|
| Absolute zero | -273.15 | -459.67 | 0 |
| Water freezing point | 0 | 32 | 273.15 |
| Room temperature (comfortable) | 20 | 68 | 293.15 |
| Human body temperature | 37 | 98.6 | 310.15 |
| Water boiling point | 100 | 212 | 373.15 |
History and Development of Temperature Scales
Celsius (°C) was proposed by Swedish astronomer Anders Celsius in 1742. Originally he defined the boiling point of water as 0°C and the freezing point as 100°C, which was later reversed by Carl Linnaeus to the current standard (freezing point 0°C, boiling point 100°C). Celsius is a derived unit of the International System of Units (SI) and is the most widely used temperature unit worldwide.
Fahrenheit (°F) was proposed by German physicist Daniel Gabriel Fahrenheit in 1724. He defined the temperature of a mixture of ice, water, and ammonium chloride as 0°F and human body temperature as 96°F (later adjusted to 98.6°F). Fahrenheit is currently used primarily in the United States, the Bahamas, the Cayman Islands, and a few other regions.
Kelvin (K) was proposed by British physicist William Thomson (Lord Kelvin) in 1848, using absolute zero (-273.15°C) as the zero point. Kelvin is the base unit of temperature in the International System of Units, denoted by the symbol K without a degree sign (°). It is widely used in physics, chemistry, astronomy, and other scientific fields. The Rankine scale (°R) and Réaumur scale (°Ré) are historically used scales that are now rarely encountered.
FAQ
°F = °C × 9/5 + 32, °C = (°F - 32) × 5/9. A quick estimation trick: Celsius to Fahrenheit—multiply by 2 and add 30 (e.g., 20°C ≈ 20×2+30 = 70°F, exact value 68°F); Fahrenheit to Celsius—subtract 30 and divide by 2 (e.g., 86°F ≈ (86-30)/2 = 28°C, exact value 30°C). The two scales are equal at -40° (-40°C = -40°F).
Absolute zero = -273.15°C = 0 K, the theoretically lowest possible temperature. At this temperature, particles cease all thermal motion and have the minimum possible energy. Kelvin to Celsius conversion: K = °C + 273.15. For example, room temperature 20°C ≈ 293.15 K, water boiling point 100°C = 373.15 K. Kelvin is a thermodynamic temperature scale with no negative values and is widely used in scientific calculations.
The Rankine scale (°R) uses Fahrenheit-sized degrees with absolute zero as its zero point, analogous to how Kelvin uses Celsius-sized degrees. °R = °F + 459.67, °F = °R - 459.67. For example, water freezing point 32°F = 491.67°R, water boiling point 212°F = 671.67°R. Rankine is primarily used in some US engineering fields and is uncommon internationally.
The Réaumur scale (°Ré) sets the freezing point of water at 0°Ré and the boiling point at 80°Ré, with °Ré = °C × 4/5. Proposed by French scientist René Antoine Ferchault de Réaumur in 1730, it was once widely used across Europe, particularly in France, Germany, and Russia. However, it was gradually replaced by Celsius during the 20th century. Today it is only occasionally used in a few traditional industries, such as cheese-making and syrup production in parts of Italy and Switzerland.
No. All conversion calculations run entirely in your browser using pure JavaScript math. Your input data never leaves your device.
This tool uses JavaScript double-precision floating-point numbers (64-bit IEEE 754) for calculations, which is sufficiently accurate for the vast majority of everyday scenarios. Temperature conversion formulas (e.g., ×9/5, +32, +273.15) are exact mathematical relationships with no approximation error. Decimal portions are capped at 6 significant decimal places, and excessively long decimals are automatically truncated. For extreme values (such as near absolute zero), there may be minor errors due to floating-point precision limitations, but this has virtually no practical impact.
It supports 5 common temperature units: Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), and Réaumur (°Ré). Enter a value in any one unit and the results for all other units are automatically calculated — no need to manually select a target unit.
No. This tool requires no registration or login to use. We provide a daily free quota for every user, sufficient to meet everyday temperature conversion needs. If you need a higher quota or more frequent use, you can upgrade to a membership to unlock more benefits.
Yes. The page uses a responsive design and works normally in browsers on phones, tablets, and computers. On mobile, just tap the input field, select a unit, and tap Convert to see the results — the operation is the same as on desktop.
Yes. Except for Kelvin (K), Celsius, Fahrenheit, Rankine, and Réaumur all support negative input. Note that Kelvin (K) and Rankine (°R) are absolute temperature scales with no negative values in theory; 0 K (absolute zero) is the lowest possible temperature. If you input such a low negative value that the Kelvin result becomes negative, that temperature is below absolute zero and does not physically exist.
They are rarely used now. The Rankine scale (°R) uses Fahrenheit-sized degrees with absolute zero as its zero point and is mainly used in some US engineering fields; it is uncommon internationally. The Réaumur scale (°Ré), proposed by French scientist René Antoine Ferchault de Réaumur in 1730, was replaced by Celsius during the 20th century and is now only occasionally used in a few traditional industries such as cheese-making and syrup production in parts of Italy and Switzerland.
Click the copy icon to the right of the result box. Each unit result has a copy button on its right; clicking it automatically copies the value to your clipboard so you can paste it into documents, reports, or spreadsheets without manually selecting the text.
Content last updated：2026-07-16
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