Temperature is the one conversion you cannot do by multiplying, and that is why the mental shortcuts everyone uses for other units fail here. The scales have different zero points as well as different step sizes.
What the Temperature Converter does
Converts between Celsius, Fahrenheit and Kelvin. Because the scales are offset, each conversion needs both a factor and an addition: °F = °C × 9/5 + 32, and K = °C + 273.15.
That offset is why doubling a temperature is meaningless. 20 °C is not twice as hot as 10 °C in any physical sense — only Kelvin, which starts at absolute zero, supports that kind of arithmetic.
Open the Temperature Converter and follow the settings and checks below.
Scales and reference points
| Setting | What it means |
|---|---|
| Celsius → Fahrenheit | × 9/5, then + 32 |
| Celsius → Kelvin | + 273.15 |
| Water freezes | 0 °C · 32 °F · 273.15 K |
| Water boils | 100 °C · 212 °F · 373.15 K |
| Absolute zero | −273.15 °C · −459.67 °F · 0 K |
| The scales cross at | −40 — the same number in °C and °F |
| Kelvin has no degree sign | Written "300 K", not "300 °K" |
| Why offsets matter | Ratios are only meaningful in Kelvin |
How to use it
- Enter the temperature.
- Choose the scale it is in.
- Read all three scales at once.
Practical advice
−40 is the same in Celsius and Fahrenheit — the point where the two scales cross. It is a useful sanity check: if you have written a conversion and it does not agree at −40, the formula is wrong. It is also why the aviation industry can quote −40 without specifying which scale.
Common questions
Why can I not just multiply to convert temperature?
Because the scales have different zero points. Length units all start at zero length, so a single factor works. Celsius starts at water freezing and Fahrenheit 32 degrees below it, so the conversion needs an addition as well as a multiplication.
Is 20 °C twice as warm as 10 °C?
No. Ratios only mean anything on a scale that starts at absolute zero, which is Kelvin. In Kelvin those two are 293.15 and 283.15 — barely 3% apart, which is much closer to how they actually feel.
Why 273.15 and not 273?
Because the Kelvin scale is defined so that water’s triple point falls at exactly 273.16 K, putting 0 °C at 273.15 K. The .15 is not a rounding artefact; dropping it introduces a real error in scientific work.
Should I write °K?
No. Kelvin is an absolute unit and takes no degree symbol — 300 K, not 300 °K. Celsius and Fahrenheit do take it.
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Vootkit provides a browser calculator and educational guidance. Results depend on the values and units you enter, so verify important financial, academic, safety or professional decisions with an appropriate authoritative source.
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