Temperature Converter — Celsius, Fahrenheit, Kelvin & Rankine
Our free temperature converter lets you convert between Celsius, Fahrenheit, Kelvin, and Rankine in real time. Type a value in any field and all three (or four) scales update simultaneously — no button press needed. All calculations run entirely in your browser; no data is sent to any server.
Choose your desired decimal precision (0–5 places) to control how results are displayed. Use Copy to copy any converted value to the clipboard in one click.
Conversion Formulas
| From → To | Formula |
|---|---|
| °C → °F | (°C × 9/5) + 32 |
| °F → °C | (°F − 32) × 5/9 |
| °C → K | °C + 273.15 |
| K → °C | K − 273.15 |
| °C → °R | (°C × 9/5) + 491.67 |
| °R → °C | (°R − 491.67) × 5/9 |
Key Reference Points
| Reference | °C | °F | K |
|---|---|---|---|
| Absolute Zero | −273.15 | −459.67 | 0 |
| Freezing Point | 0 | 32 | 273.15 |
| Body Temperature | 37 | 98.6 | 310.15 |
| Boiling Point | 100 | 212 | 373.15 |
Frequently Asked Questions
How do I use this temperature converter? Type any temperature value into the Celsius, Fahrenheit, Kelvin, or Rankine input field. All other fields update instantly. Use the precision slider to set the number of decimal places shown.
Why does −40 °F equal −40 °C? −40 is the unique point where the Celsius and Fahrenheit scales intersect. It falls out of the math: (−40 × 9/5) + 32 = −40. This fact is useful as a quick cross-check when working with both scales.
What is absolute zero? Absolute zero (0 K / −273.15 °C / −459.67 °F) is the lowest theoretically possible temperature. At this point particles have minimum thermal motion. It is physically unattainable but serves as the origin of the Kelvin and Rankine thermodynamic scales.
When is Kelvin used instead of Celsius? Kelvin is the SI base unit of temperature and is used in scientific and engineering contexts — thermodynamics, astrophysics, chemistry, and electronics. Celsius is derived from Kelvin; they share the same degree size, offset by 273.15.
What is the Rankine scale used for? Rankine is used primarily in thermodynamic engineering calculations in the United States, especially in older aerospace and mechanical engineering literature. It is to Fahrenheit what Kelvin is to Celsius.