What Is a Temperature Converter?
A temperature converter changes a reading from one scale to another, such as Celsius to Fahrenheit or Kelvin to Rankine. Most countries report weather in Celsius, the United States uses Fahrenheit, and scientists work in Kelvin. Converting by hand is slow and easy to get wrong, so this free online temperature converter does it for you the moment you type.
How to Use the TempFlow Pro Converter
Step-by-step
- Type any number, including decimals and negatives.
- Pick the unit you started with: Celsius, Fahrenheit, Kelvin or Rankine.
- Read all four results, updated live as you type.
- Choose the number of decimal places, or leave it on Auto.
- Press Reset to clear the input, presets and history.
Handy extras
- Presets load common values like freezing, body temperature and absolute zero.
- Copy puts any result on your clipboard; Use turns a result into the new input.
- Thermometer bar shows how hot or cold your value is.
- Recent conversions keep your last five results on your device only.
- Absolute-zero check warns you about impossible values.
The Four Major Temperature Scales
Celsius (°C)
Celsius is the metric scale used worldwide. Water freezes at 0°C and boils at 100°C at standard pressure, as described by the National Institute of Standards and Technology.
Fahrenheit (°F)
Fahrenheit is used mainly in the United States for weather and household temperatures. Water freezes at 32°F and boils at 212°F.
Kelvin (K)
Kelvin is the SI base unit of thermodynamic temperature. It starts at absolute zero and has no negative values, which is why physics and chemistry rely on it. See the Kelvin overview on Wikipedia.
Rankine (°R)
Rankine is an absolute scale with Fahrenheit-sized degrees, common in US thermodynamics and aerospace engineering.
Temperature Conversion Formulas
From Celsius
- °F = °C × 9/5 + 32
- K = °C + 273.15
- °R = (°C + 273.15) × 9/5
From Fahrenheit
- °C = (°F − 32) × 5/9
- K = (°F + 459.67) × 5/9
- °R = °F + 459.67
From Kelvin and Rankine
- °C = K − 273.15
- °R = K × 9/5
- K = °R × 5/9
- °F = °R − 459.67
Common Temperature Conversions
| Celsius | Fahrenheit | Kelvin | Rankine |
|---|---|---|---|
| −273.15°C | −459.67°F | 0 K | 0°R |
| −40°C | −40°F | 233.15 K | 419.67°R |
| 0°C | 32°F | 273.15 K | 491.67°R |
| 20°C | 68°F | 293.15 K | 527.67°R |
| 37°C | 98.6°F | 310.15 K | 558.27°R |
| 100°C | 212°F | 373.15 K | 671.67°R |
Real-World Uses of Temperature Conversion
Cooking and baking
Recipes use different scales for oven settings. A wrong conversion can mean a burnt or raw dish, so check the number before you preheat.
Weather and travel
Forecasts abroad may use a scale you don’t think in. Compare live conditions with the National Weather Service, and try our weather checker tool.
Science and engineering
Kelvin and Rankine are essential wherever absolute temperature is needed, from lab work to gas-law and thermodynamic calculations.
Health
Body temperature is recorded in Fahrenheit in the US and Celsius elsewhere. Normal is about 37°C or 98.6°F.
Why Use This Temperature Converter?
It is fast, accurate and private: everything runs in your browser, with no sign-up, no download and no ads. Conversions pass through Kelvin internally, so every scale agrees with every other. Explore more free utilities in the floan.in tools directory, including the area converter, the energy converter and the file size converter. Learn more on the About page.
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 and add 32. For example, 20°C × 9/5 + 32 = 68°F.
How do I convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit value, then multiply by 5/9. For example, (68°F − 32) × 5/9 = 20°C.
What is 0 Kelvin in Celsius and Fahrenheit?
0 K, absolute zero, equals −273.15°C and −459.67°F, the point where thermal motion is at its minimum.
At what temperature are Celsius and Fahrenheit equal?
At −40 degrees both scales show the same number: −40°C = −40°F.
What is the Rankine scale used for?
Rankine is an absolute scale with Fahrenheit-sized degrees, used mainly in US engineering, thermodynamics and aerospace work.
Is this temperature converter free?
Yes. It is free, works on any device and needs no sign-up or download.