Choose both scales explicitly
The Temperature Converter converts an absolute temperature between Celsius, Fahrenheit, and Kelvin. Enter the numerical Temperature, select From and To, then choose Convert / calculate. Keeping the scale beside the original value prevents a common mistake: copying a bare number into a field that assumes a different scale.
Temperature conversion includes an offset as well as a scale factor. Multiplying a Fahrenheit value by a constant alone will not generally produce Celsius. The converter first expresses the input in Celsius, then calculates the target scale from that intermediate value.
Verify a familiar room temperature
Enter 68, choose Fahrenheit in From, and Celsius in To. The expected result is:
68 Fahrenheit = 20 CelsiusThe arithmetic is (68 − 32) × 5 ÷ 9 = 20. Keep the original input at 68 Fahrenheit, change To to Kelvin, and calculate again. The expected result is 293.15 Kelvin. Alternatively, convert 20 Celsius to Kelvin and recover the same value.
These examples offer useful reference checks for the menu direction. A result such as 154.4 Fahrenheit would come from treating 68 as Celsius, which describes a different input rather than a rounding difference.
Distinguish a reading from a change
A thermometer reading of 20 Celsius is an absolute temperature. A change of 20 Celsius degrees is a difference between two readings. Offsets cancel when calculating a difference, so a temperature interval should not be passed through this absolute-temperature workflow as though it were a thermometer reading.
For two readings, convert each absolute temperature if necessary and then subtract them in a common scale. State whether your final number is a reading or a change. This distinction matters in charts and product specifications even when the visible unit labels look similar.
Interpret boundaries and precision
The tool rejects a temperature below absolute zero, allowing only a small internal tolerance for floating-point arithmetic. For example, negative Kelvin input should not produce a normal physical temperature result. A rejected value is a prompt to review the number and source scale.
Results display up to 12 significant digits. Your measurement device may justify far fewer, so round according to the source reading and the purpose of the result. The converter does not estimate instrument uncertainty or verify that a recipe, experiment, or device is suitable for a particular temperature.
All calculation happens in the browser. For length, mass, and area rather than temperature, use Unit Converter and retain the source units alongside your copied result.