What is a Temperature Converter?
A temperature converter transforms temperature measurements between different scales. Temperature measures the average kinetic energy of particles in a substance, indicating how hot or cold something is.
This converter supports four temperature scales: Celsius (°C) used globally, Fahrenheit (°F) used in the US, Kelvin (K) used in science, and Rankine (°R) used in some engineering applications.
Temperature Scales Explained
Celsius (°C): Used worldwide except in the US. Water freezes at 0°C and boils at 100°C at standard pressure. Originally called centigrade because of the 100-degree range between freezing and boiling.
Fahrenheit (°F): Used primarily in the United States. Water freezes at 32°F and boils at 212°F. Provides finer granularity in typical weather ranges without using decimals.
Kelvin (K): The SI base unit for temperature, used in science. Starts at absolute zero (0 K = -273.15°C), the coldest possible temperature. No degree symbol is used with Kelvin.
Rankine (°R): An absolute scale like Kelvin but based on Fahrenheit increments. Used in some US engineering fields. Absolute zero is 0°R = -459.67°F.
Conversion Formulas
°F = (°C × 9/5) + 32
°C = (°F - 32) × 5/9
Celsius ↔ Kelvin:
K = °C + 273.15
°C = K - 273.15
Fahrenheit ↔ Kelvin:
K = (°F + 459.67) × 5/9
°F = (K × 9/5) - 459.67
Celsius ↔ Rankine:
°R = (°C + 273.15) × 9/5
°C = (°R × 5/9) - 273.15
Common Temperature Reference Points
- Absolute Zero: -273.15°C, -459.67°F, 0 K, 0°R
- Water Freezing Point: 0°C, 32°F, 273.15 K
- Room Temperature: ~20°C, ~68°F, ~293 K
- Human Body Temperature: 37°C, 98.6°F, 310 K
- Water Boiling Point: 100°C, 212°F, 373.15 K
Quick Conversion Tips
- Celsius to Fahrenheit (mental math): Double it and add 30. Example: 20°C → (20×2)+30 = 70°F (actual: 68°F, close enough!)
- Fahrenheit to Celsius (mental math): Subtract 30 and halve it. Example: 70°F → (70-30)÷2 = 20°C
- Celsius to Kelvin: Just add 273 (or 273.15 for precision)
- Memorable fact: -40°C = -40°F (the only point where they're equal)
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
Use the formula: °F = (°C × 9/5) + 32. For example, to convert 25°C: (25 × 1.8) + 32 = 77°F. The ×9/5 multiplier accounts for the different scale sizes, and +32 adjusts for the different zero points.
Why is Fahrenheit still used in the US?
Historical reasons. When the US gained independence in 1776, Fahrenheit was the standard. While most countries switched to Celsius with the metric system adoption, the US retained Fahrenheit for everyday use. Science and medicine in the US do use Celsius.
What is absolute zero and can we reach it?
Absolute zero (0 K, -273.15°C, -459.67°F) is the lowest possible temperature where all molecular motion stops. The third law of thermodynamics states it's impossible to reach absolute zero, though scientists have gotten within a billionth of a degree.
Why doesn't Kelvin use the degree symbol?
Because Kelvin is the base SI unit for temperature, not a derived scale. We write "300 K" not "300°K," similar to how we write "5 meters" not "5° meters." Celsius and Fahrenheit use the degree symbol because they're relative scales.
At what temperature do Celsius and Fahrenheit meet?
They're equal at exactly -40 degrees (-40°C = -40°F). This can be proven mathematically by solving °C = (°C × 9/5) + 32 for °C, which yields -40.