Celsius Converter

How to use this Celsius converter

What this calculator does. This tool converts one absolute temperature entered in degrees Celsius into seven other temperature scales. It is useful for weather reports, cooking and laboratory notes, engineering specifications, classroom exercises, and checking data copied from equipment that uses a different scale. It performs mathematical scale conversion only; it does not determine whether a thermometer is calibrated, whether water will boil at a particular altitude, or whether a temperature is safe for a person, process, or material.

When to use it. Use it when a forecast is given in Celsius but you need Fahrenheit, when a scientific calculation requires kelvins, when an historical source uses Réaumur or Rømer, or when you need a consistent multi-scale table for documentation. For the official SI relationship between Celsius and kelvin, see the NIST temperature conversion guidance.

How to calculate. The calculator opens with a complete demonstration value of 20 °C, so all results and the Excel download are ready immediately.

1. Replace Temperature in Celsius with the value you want to convert. Enter a plain decimal using a period, such as 37, -40, or 21.5.
2. Read Temperature in Fahrenheit as the main result. The remaining cards show kelvins, Rankine, Delisle, Newton, Réaumur, and Rømer.
3. Review the comparison table when you need the scale name, symbol, and value together.
4. Select Download Excel to create a real .xlsx workbook containing the current input, every conversion, formulas as notes, and scenario checks.
5. Select Reset to clear the demonstration value and all results. Excel export becomes unavailable until you enter a complete valid Celsius value again.

Input guide. Temperature in Celsius is required and accepts a finite decimal number in degrees Celsius. The lowest physically meaningful absolute temperature is -273.15 °C; values below that are rejected. A realistic example is 20 °C. Increasing the input raises Fahrenheit, kelvin, Rankine, Newton, Réaumur, and Rømer, while Delisle decreases because its historical scale runs in the opposite direction. Common mistakes include typing a comma decimal such as 1,5, adding the °C symbol inside the field, or using scientific notation. Enter only the numeric value.

Output guide. Temperature in Fahrenheit is an exact scale conversion using 9/5 × °C + 32. Temperature in kelvins adds exactly 273.15 and cannot be negative for a valid physical temperature. Temperature in Rankine uses Fahrenheit-sized degrees from absolute zero. Temperature in Delisle decreases as Celsius rises. Temperature in Newton, Temperature in Réaumur, and Temperature in Rømer are historical scale equivalents. The summary pills repeat Fahrenheit, kelvin, and whether the input is at or above absolute zero. All outputs are conversions, not estimates or recommendations.

Worked example. With the startup input 20 °C, Fahrenheit is 20 × 9/5 + 32 = 68 °F. Kelvin is 20 + 273.15 = 293.15 K. Rankine is 20 × 9/5 + 491.67 = 527.67 °R. The same input gives 120 °De, 6.6 °N, 16 °Ré, and 18 °Rø. These numbers match the first screen and the startup workbook.