How to use Temperature Converter
- Under What are you converting?, choose a temperature value or a temperature change.
- Enter the Value, including a minus sign if needed.
- Choose the scales under Convert from and Convert to.
- The result and equation update as you change the values.
Example: Temperature Converter
Convert a thermometer reading at water's freezing point from Celsius to Fahrenheit.
Options
- What are you converting?
- Choose a temperature value for a thermometer reading, or a temperature change for an interval. Only a reading uses the Celsius to Fahrenheit offset.
Supported inputs and limits
Where your input is processed
This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.
Why readings and changes use different formulas
A Celsius reading becomes Fahrenheit after multiplying by 9/5 and adding 32. For a change, multiply by 9/5 without adding 32. For example, a rise of 10 Celsius degrees is a rise of 18 Fahrenheit degrees. The two modes prevent a temperature interval from being mistaken for an actual thermometer reading.
Where absolute zero changes the answer
A reading cannot be colder than 0 K, which is -273.15 C or -459.67 F. The calculator checks that boundary in temperature value mode. It does not apply the boundary to a change: a drop of 20 degrees can describe a difference even when the final reading is not supplied.
Questions about Temperature Converter
Why does 0 C become 32 F, while a change of 10 C becomes 18 F?
A reading needs the 32-degree offset: 0 x 9/5 + 32 = 32 F. A change has no starting point on the scale, so 10 x 9/5 = 18 Fahrenheit degrees. Choose the mode that matches what you measured.
Can I enter a negative temperature?
Yes. Enter a minus sign before a Celsius or Fahrenheit reading, or before a temperature change. A reading below absolute zero is rejected, but a negative change is valid.
Is a change of one kelvin the same size as one Celsius degree?
Yes. Kelvin and Celsius intervals have the same size, although their zero points differ for readings. A change of 5 K is a change of 5 C degrees.
What happens if I convert a scale to itself?
The number stays the same. The result still identifies the chosen mode, so you can check whether you meant a reading or a change.