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Results will show Celsius, Fahrenheit, Kelvin, formulas, steps, and a labeled thermometer scale.
Temperature conversion formulas
Temperature converter for Celsius, Fahrenheit, and Kelvin
This temperature converter changes a value between Celsius, Fahrenheit, and Kelvin while showing the exact formula used. It works as a Celsius to Fahrenheit calculator, Fahrenheit to Celsius calculator, Celsius to Kelvin converter, and Kelvin to Fahrenheit converter in one page.
Use it for homework, science class, weather comparisons, cooking conversions, lab values, or any situation where the same temperature needs to be read on another scale.
Celsius to Fahrenheit
F = (C x 9/5) + 32
Multiply Celsius by 9/5, then add 32.
Fahrenheit to Celsius
C = (F - 32) x 5/9
Subtract 32, then multiply by 5/9.
Celsius to Kelvin
K = C + 273.15
Kelvin starts at absolute zero, so add 273.15 to Celsius.
Visual temperature scale comparison
The three temperature scales use different numbers for the same physical points. Absolute zero is 0 K, water freezes at 0 °C or 32 °F, and water boils at 100 °C or 212 °F under standard pressure.
Worked temperature examples
| Conversion | Formula | Answer |
|---|---|---|
| 0 °C to Fahrenheit | (0 x 9/5) + 32 | 32 °F |
| 100 °C to Fahrenheit | (100 x 9/5) + 32 | 212 °F |
| 98.6 °F to Celsius | (98.6 - 32) x 5/9 | 37 °C |
| 300 K to Celsius | 300 - 273.15 | 26.85 °C |
Common conversion mistakes
- Using 9/5 backward: Celsius to Fahrenheit uses 9/5, while Fahrenheit to Celsius uses 5/9 after subtracting 32.
- Adding 32 to Kelvin: Kelvin converts through Celsius first. Do not add 32 directly to Kelvin.
- Writing degrees Kelvin: Kelvin is written as K, not °K.
- Ignoring absolute zero: temperatures below 0 K, -273.15 °C, or -459.67 °F are not physically valid.
Temperature converter FAQ
How do you convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5, then add 32. For example, 20 °C becomes 68 °F.
How do you convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit value, then multiply by 5/9. For example, 68 °F becomes 20 °C.
How do you convert Celsius to Kelvin?
Add 273.15 to the Celsius value. For example, 25 °C becomes 298.15 K.
Can Kelvin be negative?
No. Kelvin starts at absolute zero, so valid Kelvin temperatures are 0 K or higher.
What temperature is the same in Celsius and Fahrenheit?
-40 °C and -40 °F are the same temperature.
Why does Fahrenheit add 32?
The Fahrenheit and Celsius scales use different zero points. The +32 aligns the Celsius freezing point of water with 32 °F.
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Temperature references
These outside references are useful for checking temperature units, scale definitions, and practice conversions.