How to use (3 steps)
- Choose the source scale (Celsius, Fahrenheit, or Kelvin).
- Type a temperature (you can also use the up/down arrow keys) and pick the target scale.
- Read the converted value and formula below, or copy a shareable URL if you want to reopen the same setup later.
All calculations run only in your browser; no values are sent to a server.
Formulas used
Because the “zero point” differs across temperature scales, conversion uses both offsets and multiplication. This calculator first converts your input to Celsius (°C), then converts to the target scale.
- °C → °F: (°C × 9 ÷ 5) + 32
- °F → °C: (°F - 32) × 5 ÷ 9
- °C → K: °C + 273.15
- K → °C: K - 273.15
- °F → K: (°F - 32) × 5 ÷ 9 + 273.15
- K → °F: (K - 273.15) × 9 ÷ 5 + 32
Absolute zero is 0 K (−273.15°C, −459.67°F). Values below it are not allowed.
FAQ
How do you convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 and add 32. Example: 25°C → (25 × 9/5) + 32 = 77°F.
How do you convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9. Example: 77°F → (77 - 32) × 5/9 = 25°C.
How do you convert Celsius to Kelvin?
Add 273.15 to the Celsius value. Example: 25°C → 25 + 273.15 = 298.15 K.
Why do you add/subtract 273.15 for Kelvin?
Kelvin is an absolute temperature scale where 0 K is absolute zero. Celsius uses a different zero point (water’s freezing point), so the two scales are offset by 273.15.
Can you convert temperatures below absolute zero?
No. Absolute zero is 0 K (−273.15°C, −459.67°F). Values below it are physically impossible, so this converter blocks them.