Temperature Converter
Convert between 8 different temperature scales instantly. From everyday Celsius and Fahrenheit to scientific Kelvin and historical temperature scales like Réaumur and Newton.
Temperature Converter8 Scales
Convert between Celsius, Fahrenheit, Kelvin, and 5 other temperature scales with precision
Common Temperature References
Reference temperatures for everyday understanding
Physics
Science
Reference
Daily Life
Biology
Cooking
Safety
Materials
Understanding Temperature Scales
Temperature is a measure of the average kinetic energy of particles in a substance. Different temperature scales have been developed throughout history, each with its own reference points and applications. Understanding these scales is crucial for science, engineering, cooking, and everyday life.
Primary Temperature Scales
Celsius (°C)
Most widely used worldwide. Based on water's freezing (0°C) and boiling (100°C) points at standard atmospheric pressure.
Fahrenheit (°F)
Commonly used in the United States. Water freezes at 32°F and boils at 212°F. Provides finer granularity for everyday temperatures.
Kelvin (K)
The SI base unit for temperature. Starts at absolute zero (0K = -273.15°C). Essential for scientific calculations and thermodynamics.
Historical & Specialized Scales
Rankine (°R)
Absolute temperature scale using Fahrenheit degrees. Used in some engineering applications, especially in the United States.
Réaumur (°Ré)
Historical scale where water freezes at 0°Ré and boils at 80°Ré. Once used in parts of Europe, now mostly obsolete.
Newton (°N)
Devised by Isaac Newton. Water freezes at 0°N and the human body temperature is approximately 12°N. Rarely used today.
Temperature Conversion Formulas
Most Common Conversions
Celsius ↔ Fahrenheit
The most frequently used conversion worldwide.
Celsius ↔ Kelvin
Essential for scientific calculations and thermodynamics.
Complete Conversion Matrix
| From → To | Celsius | Fahrenheit | Kelvin | Rankine |
|---|---|---|---|---|
| Celsius | C | C × 9/5 + 32 | C + 273.15 | (C + 273.15) × 9/5 |
| Fahrenheit | (F - 32) × 5/9 | F | (F + 459.67) × 5/9 | F + 459.67 |
| Kelvin | K - 273.15 | K × 9/5 - 459.67 | K | K × 9/5 |
| Rankine | R × 5/9 - 273.15 | R - 459.67 | R × 5/9 | R |
Practical Applications
Cooking & Baking
Weather & Climate
Scientific Research
Industrial Processes
Medical & Biology
HVAC & Engineering
Historical Development of Temperature Scales
Early Development (1700s)
1724 - Fahrenheit Scale
Daniel Gabriel Fahrenheit created his scale using the freezing point of a salt-water mixture (0°F) and human body temperature (originally 96°F, later adjusted to 98.6°F).
1742 - Celsius Scale
Anders Celsius proposed a scale with 0° as water's boiling point and 100° as its freezing point. Carl Linnaeus later reversed this to the modern Celsius scale.
1730 - Réaumur Scale
René Antoine Ferchault de Réaumur created a scale where water freezes at 0° and boils at 80°, based on the expansion of alcohol in thermometers.
Modern Era (1800s-Present)
1848 - Kelvin Scale
William Thomson (Lord Kelvin) proposed an absolute temperature scale starting at absolute zero, based on the Celsius scale but with no negative values.
1859 - Rankine Scale
William John Macquorn Rankine created an absolute scale using Fahrenheit degrees, primarily for engineering applications in English-speaking countries.
1967 - SI System
The Kelvin was officially adopted as the SI base unit for thermodynamic temperature, making it the international standard for scientific measurements.
Common Temperature Conversion Mistakes
1. Forgetting the Offset in Celsius-Fahrenheit
Wrong: °F = °C × 9/5 (missing +32)
Correct: °F = (°C × 9/5) + 32. The +32 accounts for the different zero points of the two scales. Without it, 0°C would convert to 0°F instead of 32°F.
2. Mixing Up the Fraction (9/5 vs 5/9)
Wrong: °C = (°F - 32) × 9/5 (should be 5/9)
Remember: Use 9/5 when going FROM Celsius, use 5/9 when going TO Celsius. The Celsius scale has larger degrees (100° vs 180° between water's phase changes).
3. Confusing Absolute vs Relative Temperatures
Wrong: Converting temperature differences using the full formula
Correct: For temperature differences, only use the ratio (9/5 or 5/9) without the offset. A 10°C difference equals an 18°F difference, not 50°F.
4. Rounding Too Early
Wrong: Rounding intermediate calculations
Correct: Keep full precision during calculations and round only the final result. Early rounding can introduce significant errors, especially in scientific applications.
Temperature Extremes in Nature
Extreme Cold
Absolute Zero
-273.15°C (-459.67°F, 0K)
The theoretical temperature where all molecular motion stops. Impossible to reach, but scientists have gotten within billionths of a degree.
Coldest Natural Temperature
-89.2°C (-128.6°F)
Recorded at Antarctica's Vostok Station in 1983. The coldest temperature ever measured on Earth's surface.
Outer Space
-270.45°C (-454.81°F, 2.7K)
The cosmic microwave background radiation gives space an average temperature just above absolute zero.
Extreme Heat
Sun's Core
15,000,000°C (27,000,000°F)
The temperature at the Sun's core where nuclear fusion occurs. Hot enough to fuse hydrogen into helium.
Lightning
30,000°C (54,000°F)
Lightning channels can reach temperatures five times hotter than the Sun's surface, though only for microseconds.
Hottest Earth Temperature
54.4°C (129.9°F)
Recorded in Death Valley, California, in 1913. The highest air temperature ever reliably measured on Earth.
Related Conversion Tools
Frequently Asked Questions
Why do we have so many different temperature scales?
Different temperature scales were developed for different purposes and historical contexts. Fahrenheit was designed for weather (with 0°F being very cold and 100°F being very hot), Celsius for scientific use (based on water's properties), and Kelvin for absolute measurements starting from absolute zero.
Which countries use Fahrenheit vs Celsius?
Most of the world uses Celsius, including all of Europe, Asia, Africa, and South America. The United States, some Caribbean countries, and a few Pacific islands primarily use Fahrenheit. Scientists worldwide use Celsius and Kelvin regardless of their country's preference.
When should I use Kelvin instead of Celsius?
Use Kelvin for scientific calculations involving thermodynamics, gas laws, or when working with absolute temperatures. Kelvin is essential when temperature ratios matter or when calculations involve absolute zero. For everyday use, Celsius is more practical.
How accurate do temperature conversions need to be?
For cooking and weather, 1-2 decimal places are usually sufficient. For scientific work, maintain at least 3-4 decimal places. For precision instruments and research, use as many decimal places as your measurement accuracy requires. Our calculator provides up to 6 decimal places.
What's the difference between heat and temperature?
Temperature measures the average kinetic energy of particles in a substance, while heat is the total thermal energy transferred between objects. A cup of hot coffee has a higher temperature than a swimming pool, but the pool contains more total heat energy.
Can temperature be negative in Kelvin?
No, the Kelvin scale starts at absolute zero (0K), which is the lowest possible temperature. Negative Kelvin temperatures are impossible because they would represent less kinetic energy than no motion at all. This is why Kelvin is called an "absolute" temperature scale.