Fahrenheit to Celsius Calculator
Convert between Fahrenheit, Celsius, Kelvin, and Rankine temperature scales
How to Use
- Enter the temperature value you want to convert
- Select the source temperature scale from the dropdown
- Select the target temperature scale you want to convert to
- Click calculate to see the conversion result
- Review the conversion formula and all temperature scales
Temperature Scales
Temperature is measured using different scales around the world. The most common scales are Fahrenheit, Celsius, Kelvin, and Rankine, each with its own reference points and applications.
Understanding these different scales is important for scientific work, international travel, cooking, and weather forecasting. Each scale has its advantages and is used in specific contexts.
Fahrenheit Scale
The Fahrenheit scale was developed by Daniel Gabriel Fahrenheit in 1724. It sets the freezing point of water at 32°F and the boiling point at 212°F, with 180 degrees between these two points.
This scale is primarily used in the United States and its territories. It's also used in some Caribbean nations and for specific scientific applications. The scale is designed so that human body temperature is approximately 98.6°F.
Celsius Scale
The Celsius scale, also known as centigrade, was developed by Anders Celsius in 1742. It sets the freezing point of water at 0°C and the boiling point at 100°C, making it intuitive for everyday use.
This is the most widely used temperature scale globally, adopted by most countries for weather forecasts, cooking, and general temperature measurements. It's the standard scale in scientific contexts outside the United States.
Kelvin Scale
The Kelvin scale is the SI (International System of Units) base unit for temperature. It starts at absolute zero (0 K), the theoretical lowest possible temperature where all thermal motion ceases.
Kelvin uses the same increment size as Celsius, making conversions straightforward. It's primarily used in scientific contexts, physics, chemistry, and engineering calculations where absolute temperature measurements are required.
Rankine Scale
The Rankine scale is an absolute temperature scale that uses Fahrenheit increments. Like Kelvin, it starts at absolute zero (0°R) but maintains the degree size of the Fahrenheit scale.
This scale is primarily used in engineering applications in the United States, particularly in thermodynamics and heat transfer calculations where Fahrenheit units are preferred but absolute temperature measurements are needed.
Conversion Formulas
Here are the key conversion formulas between temperature scales:
- Fahrenheit to Celsius: (°F - 32) × 5/9 = °C
- Celsius to Fahrenheit: (°C × 9/5) + 32 = °F
- Celsius to Kelvin: °C + 273.15 = K
- Kelvin to Celsius: K - 273.15 = °C
- Fahrenheit to Kelvin: (°F + 459.67) × 5/9 = K
- Kelvin to Fahrenheit: (K × 9/5) - 459.67 = °F
- Fahrenheit to Rankine: °F + 459.67 = °R
- Rankine to Fahrenheit: °R - 459.67 = °F
Important Temperature Reference Points
| Reference Point | Fahrenheit | Celsius | Kelvin | Rankine |
|---|---|---|---|---|
| Absolute Zero | -459.67°F | -273.15°C | 0 K | 0°R |
| Freezing Point of Water | 32°F | 0°C | 273.15 K | 491.67°R |
| Room Temperature | 68-77°F | 20-25°C | 293-298 K | 527-534°R |
| Human Body Temperature | 98.6°F | 37°C | 310.15 K | 558.27°R |
| Boiling Point of Water | 212°F | 100°C | 373.15 K | 671.67°R |
Frequently Asked Questions
- What is the easiest way to convert Fahrenheit to Celsius?
- The easiest way is to subtract 32 from the Fahrenheit temperature, then multiply by 5/9. For a quick estimate, you can subtract 30 and divide by 2, though this is less accurate.
- Why do different countries use different temperature scales?
- Historical and cultural reasons. The US adopted Fahrenheit early and never switched, while most other countries adopted Celsius during metrication. Scientific work universally uses Kelvin for absolute measurements.
- What is absolute zero and why is it important?
- Absolute zero (0 K or -273.15°C) is the theoretical lowest possible temperature where all molecular motion stops. It's important because it provides a true zero point for temperature measurements, essential for thermodynamic calculations.
- When should I use Kelvin instead of Celsius?
- Use Kelvin when you need absolute temperature measurements, such as in scientific calculations, gas law problems, or when working with temperature differences in physics and chemistry. Use Celsius for everyday temperature measurements.
- Is Rankine still used today?
- Rankine is primarily used in engineering applications in the United States, particularly in thermodynamics and aerospace engineering. It's less common than the other three scales but useful when working with Fahrenheit-based absolute temperatures.