Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin and Rankine instantly. Enter a value in any unit and see it converted to all the others as you type.
🔒 Processed locally in your browser
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How to use
- Type a temperature value into the input field.
- Pick the unit that value is in — Celsius, Fahrenheit, Kelvin or Rankine.
- The converted value in every other unit updates instantly below.
- Switch the source unit at any time to convert from a different scale.
Features
- Converts between Celsius, Fahrenheit, Kelvin and Rankine at once
- Updates live as you type — no button to press
- Rejects temperatures below absolute zero with a clear message
- Includes the classic -40°C = -40°F crossover point
- 100% client-side — your input never leaves your browser
Frequently asked questions
What formulas does this converter use?
Fahrenheit = Celsius × 9/5 + 32, Kelvin = Celsius + 273.15, and Rankine = (Celsius + 273.15) × 9/5. Every conversion is computed via Celsius as the common pivot.
Why does -40°C equal -40°F?
It's the one point where the Celsius and Fahrenheit scales cross. Solving F = C × 9/5 + 32 for F = C gives C = -40, so -40 is the same reading on both scales.
Why can't I enter a negative Kelvin value?
Kelvin (and Rankine) are absolute temperature scales that start at absolute zero — the coldest physically possible temperature. A negative Kelvin value doesn't correspond to anything real, so the tool flags it instead of showing a misleading result.
What is Rankine used for?
Rankine is an absolute temperature scale that uses Fahrenheit-sized degrees, mostly seen in some US engineering and thermodynamics contexts. 0°R equals absolute zero, the same physical point as 0K.
Does this tool store or upload my data?
No. All conversions happen locally in your browser using plain arithmetic. Nothing you type is ever sent to a server or saved anywhere.