Temperature Converter

Temperature conversion formulas

This converter uses Celsius as the central reference scale and converts everything through that reference internally. The main formulas are listed below for quick reference.

Celsius-based 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
• Celsius to Rankine: R = (C + 273.15) × 9⁄5
• Rankine to Celsius: C = (R − 491.67) × 5⁄9
• Celsius to Réaumur: Re = C × 4⁄5
• Réaumur to Celsius: C = Re × 5⁄4

Derived formulas (via Celsius)

• Fahrenheit to Kelvin: K = (F − 32) × 5⁄9 + 273.15
• Kelvin to Fahrenheit: F = (K − 273.15) × 9⁄5 + 32
• Fahrenheit to Rankine: R = F + 459.67
• Rankine to Fahrenheit: F = R − 459.67
• Kelvin to Rankine: R = K × 9⁄5
• Rankine to Kelvin: K = R × 5⁄9

Understanding temperature scales

Temperature is one of the most common measurements in everyday life, but there are several different scales in use around the world. A good temperature converter lets you move between these scales without having to remember long formulas or carry a scientific calculator.

This page focuses on five major temperature scales: Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur. Celsius and Fahrenheit are familiar from daily weather reports, Kelvin and Rankine are common in scientific work, and Réaumur still appears in some historical and specialist contexts.

Celsius (°C)

The Celsius scale is part of the metric system and is used in most of the world for weather, cooking and everyday measurements. On this scale water freezes at 0 °C and boils at 100 °C at standard atmospheric pressure. The scale is linear, meaning each degree represents the same temperature difference anywhere on the scale.

Fahrenheit (°F)

Fahrenheit is widely used in the United States and a few other regions. In this system, water freezes at 32 °F and boils at 212 °F. The interval between freezing and boiling is divided into 180 equal parts, so each Fahrenheit degree is smaller than a Celsius degree. Many people find Fahrenheit convenient for day-to-day weather descriptions because the scale spreads out typical human comfort temperatures.

Kelvin (K)

Kelvin is the absolute temperature scale used in physics and engineering. It starts at absolute zero, the theoretical point at which all classical thermal motion stops. One Kelvin has the same size as one degree Celsius, but the zero is shifted: K = C + 273.15. Scientific formulas often require temperatures in Kelvin to work correctly, especially when dealing with gas laws and thermodynamic calculations.

Rankine (°R)

Rankine is similar to Kelvin but uses Fahrenheit-sized degrees. Absolute zero is 0 °R, and water freezes at 491.67 °R. Rankine is less common today but still appears in some older engineering references and in fields that historically used imperial units.

Réaumur (°Re)

The Réaumur scale was once popular in parts of Europe, especially for industrial and culinary uses. On this scale, water freezes at 0 °Re and boils at 80 °Re. Today it is mostly seen in historical documents, older recipes and some specialist thermometers, which is why it is still useful to have in a converter.

Why use an online temperature converter?

• Travel and weather – quickly translate weather forecasts between Celsius and Fahrenheit.
• Cooking and baking – convert oven temperatures from international recipes.
• Science and engineering – switch between Kelvin, Rankine and everyday scales while staying consistent in formulas.
• Education – help students understand how different temperature scales relate to each other.
• Historical research – interpret older documents that refer to temperatures in Réaumur or less common scales.

Tips for accurate temperature conversion

• Always double-check which scale is being used before you apply a formula or interpret a result.
• When working with scientific calculations, use Kelvin or Rankine as required by the formula and convert back to Celsius or Fahrenheit only at the end.
• Remember that rounding can introduce small differences, especially if you convert back and forth between several scales.
• For safety-critical applications, such as laboratory work or industrial processes, always confirm calculations with calibrated instruments.

Final note

This temperature converter is designed for convenience, learning and everyday planning. It should not replace professional measurement equipment or safety procedures. When an exact value is required for scientific, medical or industrial decisions, use this tool as a helpful guide, then verify with official instruments or standards.