Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, and Rankine temperature scales in real time. Type any value and all others update instantly. Includes common reference points (water freezing/boiling, body temperature, absolute zero) for quick orientation. Essential for cooking, science, travel, and engineering.
What does this tool do?
The Temperature Converter provides bidirectional conversion between four temperature scales. Celsius (°C) is the metric standard with water freezing at 0° and boiling at 100° at sea level. Fahrenheit (°F) is the US customary scale with water freezing at 32° and boiling at 212°. Kelvin (K) is the SI base unit for thermodynamic temperature with absolute zero at 0 K. Rankine (°R) is the absolute Fahrenheit scale used in some engineering contexts. The tool handles negative values correctly and shows the -40° point where Celsius and Fahrenheit coincide.
How it works
All conversions use exact formulas based on the defining relationships between scales. Celsius to Fahrenheit: °F = (°C × 9/5) + 32. Fahrenheit to Celsius: °C = (°F - 32) × 5/9. Celsius to Kelvin: K = °C + 273.15. Fahrenheit to Rankine: °R = °F + 459.67. The 9/5 and 5/9 factors derive from the 180 Fahrenheit degrees (212-32) versus 100 Celsius degrees between water's freezing and boiling points. The 273.15 offset is exact by the 2019 SI redefinition. Values below absolute zero are flagged as physically impossible (though the calculation proceeds).
Features
- 4 scales: Celsius, Fahrenheit, Kelvin, Rankine
- Common reference points displayed
- Absolute zero (-273.15°C / 0 K / -459.67°F)
- Handles negative values correctly
- Shows -40° where °C = °F
- Adjustable decimal precision
- Copy any value with one click
How to use
- 1
Enter temperature
Type in any scale — the temperature you know from your thermometer, weather report, or recipe.
- 2
Read all scales
All four temperature scales update instantly. Use the reference points to sanity-check your conversion.
- 3
Check special points
Note where interesting coincidences occur: -40° is the same in Celsius and Fahrenheit; 0°C = 32°F = 273.15 K.
- 4
Copy needed value
Click the scale you need for your recipe, scientific calculation, or international communication.
Common use cases
Cooking and baking
Convert oven temperatures between Celsius and Fahrenheit for international recipes and kitchen equipment.
Weather and travel
Understand weather forecasts in foreign countries and pack appropriate clothing for the actual temperature.
Scientific work
Convert between Celsius (common lab measurements) and Kelvin (thermodynamic calculations) for science and engineering.
Medical and health
Convert body temperature readings between Fahrenheit (US medical) and Celsius (international standard).
Tips & best practices
- For quick mental conversion: °C to °F, double and add 30 (approximate: 20°C ≈ 70°F actual 68°F). °F to °C, subtract 30 and halve
- Kelvin is Celsius + 273.15 exactly. 0 K is absolute zero, the theoretical lowest possible temperature
- Water freezes at 0°C / 32°F / 273.15 K and boils at 100°C / 212°F / 373.15 K at standard pressure (sea level)
- Rankine is rarely used today except in some thermodynamics engineering contexts — stick to the other three for general use