A temperature converter converts between Celsius, Fahrenheit, Kelvin, and Rankine. Enter a value, choose your units, and see the result with the exact formula used.
All Conversions
Reference Temperatures
| Temperature | °C | °F | K |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Water freezes | 0 | 32 | 273.15 |
| Room temperature | 20 | 68 | 293.15 |
| Normal body temp | 37 | 98.6 | 310.15 |
| Water boils | 100 | 212 | 373.15 |
How to Use the Temperature Converter
Select your source unit in the "From" dropdown and your target unit in the "To" dropdown. Type a temperature value and the result appears instantly along with the conversion formula. Use the swap button (⇆) to reverse the direction.
Celsius to Fahrenheit
Multiply by 9/5 (1.8) then add 32. Body temperature example: 37°C × 1.8 + 32 = 98.6°F. Water boils at 100°C = 212°F. A quick estimate: double the Celsius value and add 30 (good to ±5°F for everyday temperatures).
Fahrenheit to Celsius
Subtract 32 then multiply by 5/9 (0.5556). Example: 72°F (a warm room) → (72 − 32) × 5/9 = 22.2°C. Freezing point: 32°F = 0°C. A useful shortcut: subtract 32, halve the result for a rough Celsius estimate.
Celsius and Kelvin
Kelvin and Celsius differ by exactly 273.15. To convert: K = °C + 273.15. So 0°C = 273.15K and 100°C = 373.15K. Kelvin is used in science because it starts at absolute zero — there are no negative Kelvin values.
Rankine Scale
Rankine is used in some engineering applications in the United States. It shares the same zero point as Kelvin (absolute zero) but uses Fahrenheit-sized degrees. Convert: °R = °F + 459.67. Water boils at 671.67°R.
FAQ
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 then add 32. Formula: °F = (°C × 9/5) + 32. Example: 100°C = (100 × 1.8) + 32 = 212°F. Quick estimate: double the Celsius value and add 30.
How do I convert Fahrenheit to Celsius?
Subtract 32 then multiply by 5/9. Formula: °C = (°F − 32) × 5/9. Example: 98.6°F = (98.6 − 32) × 5/9 = 37°C (normal body temperature).
What is absolute zero?
Absolute zero is the coldest possible temperature: 0 Kelvin = −273.15°C = −459.67°F = 0 Rankine. At this point, all thermal motion stops. It has never been fully achieved in practice.
What is the Kelvin scale?
Kelvin is the SI unit of temperature, starting at absolute zero. Unlike Celsius and Fahrenheit, Kelvin has no negative values. Water freezes at 273.15K and boils at 373.15K.
What is the Rankine scale?
Rankine is an absolute temperature scale like Kelvin, but using Fahrenheit-sized degrees. 0°R = absolute zero. Water freezes at 491.67°R and boils at 671.67°R. Used in some engineering fields in the US.
What temperature is the same in Celsius and Fahrenheit?
−40 degrees is the same in both Celsius and Fahrenheit. At −40°C = −40°F, the two scales intersect. This is useful to remember as a quick sanity check for conversions.
Is this temperature converter free?
Yes, completely free with no signup required. All conversions happen in your browser — no data is sent to any server.