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Temperature is the only conversion here with an offset, which is why it cannot be done by multiplying. Fahrenheit and Celsius are related by F = C x 9/5 + 32, so the two scales meet at exactly -40 and nowhere else. Kelvin carries no degree sign and no negative values: 0 K is absolute zero, and converting to or from it is a matter of adding or subtracting 273.15.
The practical anchors: Fahrenheit suits how weather and bodies feel, with 0 F bitter and 100 F baking, while Celsius suits science, where water freezes at 0 and boils at 100. The common trap is reading 1 C = 33.8 F as a rate. That is a reading, not a scale factor: a rise of 1 C is a rise of 1.8 F, and a rise of 1 F is a rise of 0.556 C.
| °C | °F | K | |
|---|---|---|---|
| 1 °C | 1 | 33.8 | 274.15 |
| 1 °F | -17.222222 | 1 | 255.927778 |
| 1 K | -272.15 | -457.87 | 1 |
How do I convert Celsius to Fahrenheit? Multiply by 9, divide by 5, then add 32. So 20 C is 20 x 9 / 5 + 32 = 68 F. For a fast estimate, double the Celsius reading and add 30.
At what temperature are Celsius and Fahrenheit the same? -40. It is the single point where the two scales cross, which makes it the standard sanity check for any temperature converter.
Is 1 C the same as 33.8 F? As a reading, yes - 1 C is 33.8 F. But 33.8 is not a conversion factor. A change of 1 C equals a change of 1.8 F, and a change of 1 F equals 0.556 C.
Why is kelvin used instead of Celsius? Because it starts at absolute zero, where molecular motion bottoms out, so no negative values exist and ratios are meaningful. Double a temperature in kelvin and you really have doubled the thermal energy.
What is normal body temperature? About 37 C, which is 98.6 F - an average rather than a fixed value. Normal body temperature drifts between roughly 36.1 C and 37.2 C (97 F to 99 F) across a day and varies with the measurement site, which is why 37.2 C is not automatically a fever.