Temperature Converter
Convert Celsius, Fahrenheit, Kelvin, and Rankine. Negative Celsius and Fahrenheit are allowed; Kelvin and Rankine cannot go below absolute zero.
What Is Temperature Conversion?
Temperature conversion changes a reading from one scale to another. This converter supports Celsius (°C), Fahrenheit (°F), Kelvin (K), and Rankine (°R). Celsius and Fahrenheit are everyday weather and cooking scales. Kelvin is the SI thermodynamic scale. Rankine uses Fahrenheit-sized degrees starting at absolute zero and is used in some engineering work.
Absolute Zero
Absolute zero is the lowest possible temperature. It is 0 K, 0 °R, −273.15 °C, and −459.67 °F. This tool rejects Kelvin or Rankine values below zero, and it also rejects Celsius or Fahrenheit values that would fall below absolute zero. Negative Celsius and Fahrenheit are allowed when they are still physically possible (for example −40 °C).
How to Use This Converter
- Enter a value — Changing the value does not update the displayed result yet.
- Select From — Choose Celsius, Fahrenheit, Kelvin, or Rankine. The displayed result stays unchanged until you convert.
- Select To — Choose the scale you want. The displayed result still waits for Convert.
- Click Convert or press Enter — Calculate the result.
- Swap — Reverse the From and To scales and convert using the current value.
- Copy Result — Copy the currently displayed conversion result.
- Reset — Restore the default 0 °C to °F conversion.
Supported Temperature Scales
| Scale | Symbol | Notes |
|---|---|---|
| Celsius | °C | Water freezes at 0 °C and boils at 100 °C (at standard pressure). Negative values are valid. |
| Fahrenheit | °F | Water freezes at 32 °F and boils at 212 °F. Negative values are valid. |
| Kelvin | K | SI thermodynamic scale. 0 K is absolute zero. Values below 0 K are rejected. |
| Rankine | °R | Absolute scale with Fahrenheit-sized degrees. 0 °R is absolute zero. Values below 0 °R are rejected. |
Conversion Formulas
- °F = (°C × 9/5) + 32
- °C = (°F − 32) × 5/9
- K = °C + 273.15
- °C = K − 273.15
- °R = (°C + 273.15) × 9/5
- °R = °F + 459.67
- K = °R × 5/9
Common Temperature Conversions
| Description | °C | °F | K | °R |
|---|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 | 0 |
| Water freezes | 0 | 32 | 273.15 | 491.67 |
| −40 (same on C and F) | −40 | −40 | 233.15 | 419.67 |
| Typical room temperature | 21 | 69.8 | 294.15 | 529.47 |
| Water boils | 100 | 212 | 373.15 | 671.67 |
Practical Uses
- Weather: Convert international forecasts between Celsius and Fahrenheit.
- Cooking: Convert oven settings between °C and °F.
- Science: Convert lab readings to Kelvin.
- Engineering: Convert between Kelvin and Rankine in thermodynamics.
- Travel: Compare local temperature scales.
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
Use °F = (°C × 9/5) + 32. Enter a Celsius value, set From to Celsius and To to Fahrenheit, then click Convert or press Enter.
What is 0°C in Fahrenheit?
0 °C = 32 °F. That is the default conversion on this page.
What is absolute zero?
Absolute zero is 0 K, which is −273.15 °C, −459.67 °F, and 0 °R. Nothing can be colder than this on a thermodynamic scale.
Can this converter convert Kelvin?
Yes. Kelvin is included. Values below 0 K are rejected.
What is Rankine?
Rankine (°R) is an absolute temperature scale that uses the same degree size as Fahrenheit. 0 °R is absolute zero, and 0 °F = 459.67 °R.
Can I enter negative Celsius or Fahrenheit values?
Yes. Negative °C and °F are allowed when they are still at or above absolute zero. For example −40 °C = −40 °F. Values that would be below 0 K are rejected.