Temperature

Decoding Temperature: From Freezing to Fiery

Temperature is a measure of the average kinetic energy of the atoms or molecules in a substance—in simpler terms, it's a measure of how hot or cold something is. It's a fundamental physical quantity that governs everything from weather patterns and cooking processes to the state of matter itself and the rate of chemical reactions. Unlike measurements like length or weight where the zero point is absolute, temperature scales can have arbitrary zero points. This, along with different interval sizes between degrees, makes a dedicated converter essential for accurate translations between scales.

This converter is designed to handle the nuances of the most common temperature scales used around the world. Whether you're a cook in the US trying to follow a European recipe written in Celsius, a traveler checking the weather forecast abroad, a student in a science lab working in Kelvin, or an engineer using the Rankine scale, our tool ensures you can convert temperatures accurately and instantly. We support Celsius, the global standard for science and most countries; Fahrenheit, used primarily in the United States; Kelvin, the absolute scale for science; and Rankine, the absolute scale corresponding to Fahrenheit used in some engineering fields.

Fundamental Temperature Conversion Formulas

• 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
• Fahrenheit to Rankine: °R = °F + 459.67
• Ideal Gas Law (Chemistry/Physics): The Ideal Gas Law, PV = nRT, shows the direct relationship between pressure (P), volume (V), and absolute temperature (T). Temperature must be in an absolute scale (Kelvin or Rankine) for this formula to work correctly.
• Thermal Expansion (Physics): The change in length (ΔL) of a material due to a change in temperature (ΔT) is given by ΔL = αL₀ΔT, where L₀ is the original length and α is the coefficient of linear expansion.

A Deep Dive into Common Temperature Scales

• Celsius (°C): Part of the metric system, the Celsius scale was developed by Swedish astronomer Anders Celsius in 1742. It is the standard for temperature measurement in most of the world. It is a relative scale defined with 0°C as the freezing point of water and 100°C as the boiling point of water at one standard atmosphere of pressure. Its intuitive, water-based reference points make it easy to understand for everyday use.
• Fahrenheit (°F): Developed by physicist Daniel Gabriel Fahrenheit in 1724, this scale is used primarily in the United States, its territories, and a few other countries. On the Fahrenheit scale, the freezing point of water is 32°F and the boiling point is 212°F. While less common globally, it remains deeply embedded in American daily life, from weather reports to oven settings.
• Kelvin (K): The base unit of temperature in the International System of Units (SI), proposed by William Thomson, Lord Kelvin, in 1848. The Kelvin scale is an absolute temperature scale, meaning its zero point, 0 K, is absolute zero—the theoretical point at which all atomic motion and thermal energy cease. Kelvin is used extensively in scientific and engineering fields. The size of one kelvin is the same as one degree Celsius, making conversions between them a simple addition or subtraction.
• Rankine (°R): Developed by Scottish engineer and physicist William John Macquorn Rankine in 1859, this is an absolute temperature scale related to Fahrenheit in the same way Kelvin is related to Celsius. Its zero point is absolute zero (0°R), and the size of one Rankine degree is the same as one Fahrenheit degree (°R = °F + 459.67). It is used in some specific fields of engineering, particularly thermodynamics, in the United States.
• Réaumur (°Ré): Developed by René Antoine Ferchault de Réaumur in 1730, this scale sets the freezing point of water at 0°Ré and the boiling point at 80°Ré. It saw some use in Europe, particularly in France and Germany, but is now largely obsolete.
• Rømer (°Rø): One of the earliest temperature scales, created by Danish astronomer Ole Rømer in 1701. It set the freezing point of brine at 0°Rø, the freezing point of water at 7.5°Rø, and the boiling point of water at 60°Rø. It was a precursor to the Fahrenheit scale.
• Newton (°N): Devised by Sir Isaac Newton around 1700. He set the freezing point of water at 0°N and the boiling point at 33°N. It was a crude early attempt and never saw widespread use.
• Delisle (°De): An unusual scale invented by French astronomer Joseph-Nicolas Delisle in 1732. It is an inverted scale where the zero point is the boiling point of water (0°De) and the freezing point is 150°De. It was used in Russia for some time.