Unit category

Temperature Units and Conversions

Convert between Celsius, Fahrenheit, Kelvin, Rankine and Réaumur, with the formulas and scale differences needed for weather, cooking, science and engineering.

Convert all Temperature units

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33.8 °F
1 °C = 33.8 °F

1 °C in every unit

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Detailed guide to Temperature

Temperature indicates thermal state and is one of the most widely used measured quantities in engineering, science and everyday life.

Unlike purely proportional unit families, temperature conversions may include an offset as well as a scale factor.

Physical quantity
Temperature
SI base unit
Kelvin
Common engineering scale
Celsius
Typical offset example
0 °C = 273.15 K
Typical use
Weather, process control and thermodynamics

Temperature scale context

Celsius is used for weather and everyday temperatures in most countries, while Fahrenheit is common in the United States. Kelvin is the absolute scale used in scientific work.

Temperature intervals are not converted with the same offset as absolute temperatures. Use a dedicated temperature converter rather than applying a simple ratio.

What is temperature?

Temperature represents the thermal condition of a body or environment.

It is used in weather data, materials, energy systems, fluid properties and laboratory work.

Celsius, Fahrenheit and Kelvin

Celsius is widely used in daily and engineering practice. Fahrenheit remains common in some countries, while Kelvin is the SI base unit used in science and thermodynamics.

Kelvin and Celsius share the same interval size, but Kelvin starts from absolute zero. A temperature of 0 °C is exactly 273.15 K, while water freezes at 32 °F on the Fahrenheit scale.

Temperature conversion formulas

To convert Celsius to Fahrenheit, multiply by 1.8 and add 32: °F = (°C × 1.8) + 32. To convert Fahrenheit to Celsius, subtract 32 and divide by 1.8: °C = (°F − 32) ÷ 1.8.

Kelvin uses an absolute zero point: K = °C + 273.15 and °C = K − 273.15. The converter applies these offsets automatically, so the result is not limited to simple multiplication.

Why are temperature conversions special?

Temperature scales do not always share the same zero point, so some conversions require both multiplication and addition or subtraction.

This is why Celsius-to-Fahrenheit and Celsius-to-Kelvin formulas differ from simple proportional conversions such as length or mass. For example, 20 °C is not twice as warm as 10 °C in an absolute physical sense because Celsius has an offset zero point.

Temperature values and temperature differences

A temperature value identifies a point on a scale, so the offset between Celsius, Fahrenheit and Kelvin matters. A temperature difference is an interval, such as a rise of 10 degrees during heating.

A difference of 1 °C has the same size as a difference of 1 K. A difference of 1 °F is smaller: it equals 5/9 of a Celsius or kelvin interval. This distinction matters in heat-transfer, material and engineering calculations.

Rankine and Réaumur

Rankine is an absolute temperature scale with degree steps the same size as Fahrenheit degrees. It is encountered in some US and imperial engineering contexts; 0 °R is absolute zero.

Réaumur is a historical scale that set water's freezing point to 0 °Ré and its boiling point to 80 °Ré. It is uncommon in modern work, but it can appear in older scientific, industrial and culinary sources.

Unit comparison table

UnitSymbolSI equivalentSystemCommon use
Celsius°C0 °C = 273.15 KMetric/internationalWeather, cooking and engineering
Fahrenheit°F32 °F = 0 °CUS customary useUS weather, cooking and household settings
KelvinK0 K = absolute zeroSI base unitScience, thermodynamics and absolute temperature
Rankine°R0 °R = absolute zeroFahrenheit-based absolute scaleUS and imperial engineering references
Réaumur°Ré0 °Ré = 0 °C; 80 °Ré = 100 °CHistorical scaleOlder scientific, industrial and culinary sources

Temperature units

UnitSymbolInformation
Celsius°CView unit guide
Fahrenheit°FView unit guide
KelvinKView unit guide
Rankine°RView unit guide
Réaumur°RéView unit guide

Sources

  1. BIPM: The International System of Units (SI Brochure)
  2. NIST: Guide for the Use of the International System of Units

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