Temperature Converter: Celsius, Fahrenheit

What Is the Temperature Converter?

The Temperature Converter instantly converts any temperature from one of four commonly used scales (Celsius, Fahrenheit, Kelvin, or Rankine) into all three others simultaneously. This makes it ideal for everyday conversions between Celsius and Fahrenheit (recipe temperatures, weather, travel) as well as scientific conversions involving Kelvin and Rankine.

Unlike simple lookup tables that only handle common values, this converter calculates precisely for any input, including decimals and negative temperatures.

Key Features

• Convert between four temperature scales: Celsius, Fahrenheit, Kelvin, and Rankine.
• Instant conversion: Results for all four scales appear simultaneously from a single input.
• Scientific precision: Full floating-point precision suitable for scientific calculations.

The Four Temperature Scales

Celsius (°C): The dominant scale for everyday temperature worldwide. Water freezes at 0°C and boils at 100°C at standard atmospheric pressure.

Fahrenheit (°F): Used for everyday temperatures in the United States. Water freezes at 32°F and boils at 212°F. Notably, -40°F equals -40°C: the only point where both scales intersect.

Kelvin (K): The absolute temperature scale used in physics and engineering. Zero Kelvin (absolute zero) is -273.15°C or -459.67°F. Each Kelvin equals one Celsius degree in magnitude, just shifted by 273.15.

Rankine (°R): An absolute scale like Kelvin, but using Fahrenheit-sized degrees. Zero Rankine is absolute zero. Rankine is used in some US engineering and thermodynamics contexts where Fahrenheit conventions dominate.

How to Use the Temperature Converter

Step 1: Enter the Temperature

Type any numeric value (whole numbers, decimals, or negative values) into the Temperature field.

Step 2: Select the Source Scale

Choose Celsius, Fahrenheit, or Kelvin from the From Scale selector. (Rankine can be selected if you are starting from a Rankine value.)

Step 3: Read All Four Results

Click Calculate to see the temperature converted into all four scales:

• Celsius (°C)
• Fahrenheit (°F)
• Kelvin (K)
• Rankine (°R)

Conversion Formulas Reference

For those who want to understand the math:

Celsius to Fahrenheit: F = (C × 9/5) + 32 Fahrenheit to Celsius: C = (F − 32) × 5/9 Celsius to Kelvin: K = C + 273.15 Kelvin to Celsius: C = K − 273.15 Celsius to Rankine: R = (C + 273.15) × 9/5 Rankine to Celsius: C = (R × 5/9) − 273.15

Practical Examples

Example 1: Recipe Oven Temperature An American recipe calls for 350°F. Convert to Celsius for a metric-calibrated oven: approximately 177°C.

Example 2: Travel Weather Traveling from Europe (25°C expected) to the US. Convert: 25°C = 77°F, a warm summer day.

Example 3: Science Problem A gas law problem states temperature as 500 K. Convert to Celsius (226.85°C) or Fahrenheit (440.33°F) for context.

Example 4: Absolute Zero Enter 0 K. Results: -273.15°C, -459.67°F, 0°R.

Example 5: Extreme Heat The surface of the Sun is approximately 5,500°C. Convert to Fahrenheit (9,932°F) and Kelvin (5,773 K).

Tips and Best Practices

Quick mental estimates for Celsius to Fahrenheit: Double the Celsius temperature and add 30. This gives an approximate Fahrenheit value within a few degrees for the typical range of weather temperatures. For more precise values, use the converter.

Temperature below absolute zero is impossible: Kelvin values cannot be negative in the physical world. If a calculation produces negative Kelvin, there is an error in the input or formula.

Medicine uses Celsius internationally: Body temperature of 37°C (98.6°F) is the human average. A fever is generally defined as above 38°C (100.4°F).

Cooking precision matters: Ovens calibrated in Fahrenheit and recipes written in Celsius (or vice versa) require accurate conversion. A 20°C error in oven temperature can significantly affect baking results.

Common Issues and Troubleshooting

Very large or very small numbers in Kelvin output. Kelvin is always positive and starts from 0 at absolute zero. Common everyday temperatures (like -30°C) convert to large positive Kelvin values (243.15 K), which can seem counterintuitive.

Results seem imprecise for scientific work. This converter provides standard floating-point precision. For very high-precision thermodynamic calculations (where temperature uncertainty in the sixth decimal place matters), reference a dedicated scientific resource.

Privacy and Security

All conversions run locally in your browser. No data is transmitted or stored.

Frequently Asked Questions

What temperature is the same in both Celsius and Fahrenheit? -40 degrees. At -40°C = -40°F, both scales intersect. This is a useful fact for extreme cold weather comparisons.

Why is Kelvin written without a degree symbol? By convention, Kelvin temperatures are written as "300 K" not "300°K." The degree symbol is used for Celsius, Fahrenheit, and Rankine but not Kelvin, reflecting its status as an absolute SI unit.

What is 37°C in Fahrenheit? 98.6°F: normal human body temperature.

What is 100°C in Kelvin? 373.15 K: the boiling point of water at standard atmospheric pressure.

Is Rankine used anywhere today? Rankine is used in some US engineering fields, particularly thermodynamics, aerospace engineering, and chemical engineering contexts where calculations use Fahrenheit but require an absolute temperature scale.

Related Tools

• Coming Soon: Temperature Calculator: Convert between all 8 temperature scales including historical ones like Réaumur, Delisle, Newton, and Rømer.
• Speed Converter: Convert between m/s, km/h, mph, knots, ft/s, and Mach.