Supported units
- Celsius (°C)
- Fahrenheit (°F)
- Kelvin (K)
Conversion tool
Temperature Converter
Select a category, enter a value, and convert between compatible units.
Temperature units explained
Temperature indicates the thermal state of a substance or system. Celsius, Fahrenheit and kelvin use different reference points, so temperature conversion requires more than a simple multiplication factor.
Common engineering uses
Temperature conversion is important in thermal engineering, HVAC, laboratories, manufacturing processes and weather data.
Formula
°F = (°C × 9/5) + 32; K = °C + 273.15
Temperature scales use different zero points as well as different interval sizes. Celsius and kelvin have equal interval sizes, while one Celsius degree of temperature difference equals 1.8 Fahrenheit degrees.
- °C = temperature in degrees Celsius
- °F = temperature in degrees Fahrenheit
- K = absolute temperature in kelvin
Common conversions
| From | Equivalent value |
|---|---|
| −40 °C | −40 °F = 233.15 K |
| 0 °C | 32 °F = 273.15 K |
| 20 °C | 68 °F = 293.15 K |
| 37 °C | 98.6 °F = 310.15 K |
| 100 °C | 212 °F = 373.15 K |
| Temperature difference of 1 °C | Difference of 1 K = 1.8 °F |
Convert 68 °F to °C
- Subtract 32 from the Fahrenheit temperature.
- Multiply the result by 5/9.
- (68 − 32) × 5/9 = 20 °C.
68 °F = 20 °C
The offset of 32 applies to temperature values, not to temperature differences.
Engineering applications
- HVAC and refrigeration design, testing and maintenance.
- Monitoring manufacturing, heat-treatment and chemical processes.
- Thermodynamic calculations that require absolute temperature in kelvin.
- Comparing material properties and equipment ratings given at different temperatures.
- Converting laboratory, weather and international technical data.
Common mistakes
- Using only a multiplication factor for Celsius-to-Fahrenheit conversion and forgetting the 32-degree offset.
- Applying the 32-degree offset to a temperature difference.
- Writing degrees kelvin. The unit name and symbol are kelvin and K, without a degree sign.
- Using Celsius instead of kelvin in formulas that require absolute temperature.
- Reporting more decimal places than the accuracy of the sensor or original measurement supports.
Frequently asked questions
At what temperature are Celsius and Fahrenheit equal?
The two scales have the same numerical value at −40: −40 °C equals −40 °F.
How do I convert Celsius to kelvin?
Add 273.15 to the Celsius value. For example, 20 °C equals 293.15 K.
Does one degree Celsius equal one kelvin?
A temperature difference of 1 °C equals a difference of 1 K, but the scales have different zero points.
Can kelvin temperatures be negative?
Not on the thermodynamic temperature scale: 0 K is absolute zero.
Why is temperature conversion not always linear multiplication?
Celsius and Fahrenheit use different interval sizes and different zero points, so both scaling and an offset are required.