Overview
Convert between Celsius, Fahrenheit, Kelvin and Rankine with live two-way updates and the formulas shown on the page. Type a value in any scale and see all four at once, with common reference points for sanity-checking. Useful for cooking, science homework, hardware specs and weather reports from other countries, and it runs entirely offline.
How It Works
Enter a value and pick the scale you are converting from using the four buttons. The page immediately displays the equivalent in all four scales - Celsius, Fahrenheit, Kelvin and Rankine - each in its own card with two-decimal precision; the scale you typed in is dimmed. Reference points are built in: body temperature, water's freezing and boiling points and room temperature are the anchors most people need. Change the number or the source scale and every card refreshes simultaneously.
Step-by-Step Usage Guide
- Type the temperature value.
- Press the button for the scale you entered.
- Read all four converted values in the result cards.
- Use the reference points to sanity-check, for example 37C body temperature.
Technical Specifications & Standards
The implementation is a hub-and-spoke design: any input is first normalised to Celsius, then expanded to the other three scales, which means only six formulas need to be right instead of twelve pairwise ones. From Celsius: Fahrenheit is C x 9/5 + 32, Kelvin is C + 273.15, and Rankine is C x 9/5 + 491.67 - Rankine being the Fahrenheit-scale analogue of Kelvin, with its zero at absolute zero, which is why it appears mostly in thermodynamics and some US engineering fields. Kelvin conversion is exact by definition since the kelvin is an SI base unit and the degree Celsius is defined relative to it; the 273.15 offset is exact, not rounded. Two honest caveats: the tool does not clamp physically impossible inputs, so you can convert a temperature below absolute zero, and results are displayed to two decimals regardless of how many significant figures the input justifies - 0.1C of input precision does not become 0.01C of real precision in the output.
Targeted Use Cases
- Converting an oven or recipe temperature between Celsius and Fahrenheit.
- Interpreting a US weather forecast for a metric reader.
- Science and engineering coursework moving between Kelvin and Celsius.
- Reading hardware datasheets that quote operating ranges in Fahrenheit or Rankine.
Notes & Gotchas
- Sanity-check against the reference points before trusting a surprising result.
- Remember Kelvin and Rankine have no degree symbol in formal writing, even though the cards label them uniformly.
- Do not treat extra decimal places as extra precision - the output mirrors your input's real accuracy.
- For below-absolute-zero inputs the maths runs but the physics does not; such values are typos.
Frequently Asked Questions
What is Rankine and when is it used?
Rankine is an absolute scale like Kelvin but with Fahrenheit-sized degrees; its zero is absolute zero. It appears in some US thermodynamics and engineering contexts, and this page converts it via Celsius like the others.
How are the conversions computed?
Every input is normalised to Celsius first, then converted to the other three scales. That keeps the formula set small and consistent regardless of which pair of scales you choose.
Can I convert below absolute zero?
The arithmetic will run, but physically no temperature exists below 0 K (minus 273.15 C). A result there means the input was a typo.
Why do results show two decimals?
Two-decimal display keeps the four cards aligned and readable. It reflects display formatting, not added measurement precision.