Temperature Converter

Free temperature conversion tools. Convert between Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur — plus advanced thermal engineering unit converters.

Basic Temperature Converters

• Celsius to Fahrenheit
• Fahrenheit to Celsius
• Celsius to Kelvin
• Kelvin to Celsius
• Fahrenheit to Kelvin
• Kelvin to Fahrenheit
• Rankine to Kelvin
• Réaumur to Kelvin

Thermal Engineering Converters

• Triple Point of Water to Kelvin (273.16 K)
• Temperature Interval (?T) Converter
• Thermal Expansion Converter
• Thermal Resistance Converter (R-value)
• Thermal Conductivity Converter
• Specific Heat Capacity Converter
• Heat Density Converter
• Heat Flux Density Converter
• Heat Transfer Coefficient Converter

The Three Temperature Scales

Three scales are in common use. Celsius (°C) is the world standard — water freezes at 0 °C and boils at 100 °C at sea level. Fahrenheit (°F) is used in the US; water freezes at 32 °F and boils at 212 °F. Kelvin (K) is the SI unit used in science, starting at absolute zero (−273.15 °C). Quick mental conversions: °C × 2 + 30 ≈ °F; add 273.15 to Celsius to get Kelvin. Body temperature is 37 °C = 98.6 °F = 310.15 K.

Temperature Conversion Formulas

The Four Main Temperature Scales

The Celsius scale (°C) is used worldwide for everyday temperatures, with 0°C at water's freezing point and 100°C at boiling. The Fahrenheit scale (°F) is used in the US, with 32°F at freezing and 212°F at boiling. The Kelvin scale (K) is the SI unit for thermodynamic temperature, starting at absolute zero (0 K = −273.15°C) with no negative values. The Rankine scale (°R) is the absolute scale based on Fahrenheit degrees, used in some US engineering fields: 0°R = 0 K = −459.67°F.

The conversion formulas: °F = (°C × 9/5) + 32; °C = (°F − 32) × 5/9; K = °C + 273.15; °R = °F + 459.67. The Celsius and Kelvin scales have identical degree sizes, only shifted by 273.15. The Fahrenheit and Rankine scales share the same degree size. Temperature conversions are needed when working with international equipment, scientific data, or cooking across different recipe traditions.

Temperature Scale Comparison

Choosing the Right Temperature Scale for Your Task

Three temperature scales are in common use worldwide: Fahrenheit (°F), Celsius (°C), and Kelvin (K). Fahrenheit is the everyday standard in the United States, used for weather forecasts, cooking, and body temperature. Celsius is the everyday standard everywhere else and is used in science worldwide. Kelvin is the absolute thermodynamic scale used in physics, chemistry, and engineering; it has no negative values because 0 K is absolute zero. The relationships are: °C = (°F − 32) × 5/9; K = °C + 273.15; °F = °C × 9/5 + 32. Understanding which scale a data source uses prevents dangerous errors in engineering, pharmacy, and food safety contexts. A temperature labeled “350” means very different things in Fahrenheit (oven temperature) versus Kelvin (77°C, well below boiling water).

Temperature Scale Reference Table