Temperature is one of the most commonly measured physical quantities, yet different parts of the world use different temperature scales. Understanding how to convert between Celsius, Fahrenheit, and Kelvin is essential for science, travel, cooking, and everyday life.
Quick Summary
Three main temperature scales are used worldwide: Celsius (metric system), Fahrenheit (US customary), and Kelvin (scientific absolute scale). Each has its own conversion formulas and specific use cases.
Understanding the Three Main Temperature Scales
��C Celsius
0��C: Water freezes
100��C: Water boils
Used in most countries
��F Fahrenheit
32��F: Water freezes
212��F: Water boils
Used in USA, Bahamas
K Kelvin
0K: Absolute zero
273.15K: Water freezes
Scientific scale
Temperature Conversion Formulas
| Conversion | Formula | Example |
|---|---|---|
| Celsius to Fahrenheit | ��F = (��C �� 9/5) + 32 | 20��C = (20 �� 9/5) + 32 = 68��F |
| Fahrenheit to Celsius | ��C = (��F - 32) �� 5/9 | 68��F = (68 - 32) �� 5/9 = 20��C |
| Celsius to Kelvin | K = ��C + 273.15 | 20��C = 20 + 273.15 = 293.15K |
| Kelvin to Celsius | ��C = K - 273.15 | 293.15K = 293.15 - 273.15 = 20��C |
| Fahrenheit to Kelvin | K = (��F - 32) �� 5/9 + 273.15 | 68��F = (68 - 32) �� 5/9 + 273.15 = 293.15K |
Key Temperature Reference Points
| Description | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute Zero | -273.15��C | -459.67��F | 0K |
| Water Freezes | 0��C | 32��F | 273.15K |
| Room Temperature | 20-25��C | 68-77��F | 293-298K |
| Human Body | 37��C | 98.6��F | 310.15K |
| Water Boils | 100��C | 212��F | 373.15K |
Practical Applications
Cooking and Baking
Most recipes use either Celsius or Fahrenheit. Knowing how to convert between them is crucial for international recipes:
- 180��C = 350��F - Common baking temperature
- 200��C = 400��F - Roasting vegetables
- 220��C = 425��F - Pizza baking
Weather Forecasting
Different countries report weather in different scales. Quick mental conversions:
- 0��C = 32��F - Freezing point
- 10��C = 50��F - Cool day
- 20��C = 68��F - Room temperature
- 30��C = 86��F - Warm day
Quick Conversion Tip
For a rough Celsius to Fahrenheit conversion: Double the Celsius, subtract 10%, add 32. Example: 20��C �� 40 - 4 + 32 = 68��F (exact conversion gives 68��F).
Frequently Asked Questions
The Fahrenheit scale was created by Daniel Gabriel Fahrenheit in 1724. He originally set 0��F as the temperature of a brine solution (ice, water, and ammonium chloride) and 96��F as human body temperature. The scale was later redefined with water freezing at 32��F and boiling at 212��F, creating the 180-degree difference between these points.
Absolute zero (0K or -273.15��C) is the theoretical lowest possible temperature where all molecular motion ceases. It's a fundamental concept in thermodynamics and serves as the baseline for the Kelvin scale, which is used in scientific calculations because it starts at absolute zero and has no negative values.
Scientists prefer Kelvin because it's an absolute temperature scale that starts at absolute zero. This makes it ideal for scientific calculations, particularly in physics and chemistry, where temperature ratios and differences matter more than specific values. Unlike Celsius, Kelvin has no negative numbers, which simplifies many mathematical operations.
Recent studies suggest that average human body temperature may be slightly lower than the traditional 98.6��F (37��C). Modern research indicates normal body temperature ranges from about 97.5��F to 98.9��F (36.4��C to 37.2��C), varying by individual, time of day, and measurement method.
For a quick estimate: Celsius to Fahrenheit - Double the Celsius, subtract 10%, then add 32. Fahrenheit to Celsius - Subtract 32, then take half of that number, and add 10%. These approximations are usually within 1-2 degrees of the actual conversion for common temperatures.
Water boils at different temperatures primarily due to atmospheric pressure differences. At sea level, water boils at 100��C (212��F), but at higher altitudes where atmospheric pressure is lower, water boils at lower temperatures. For every 500-foot increase in elevation, the boiling point decreases by about 1��F (0.56��C).