# What is the value of absolute zero: $-273.15\ \rm °C$ or $-273.16\ \rm °C$?

What is the value of absolute zero?

0K= -273.15 °C Or -273.16 °C

It has been confused in different scientific scriptures. The first definition on Dictionary.com, for example.

• The triple point is the reference. It is at 0.01 C, probably that is where the confusion comes from. – Pieter Sep 2 '18 at 9:59
• @user54826 I think it's an acceptable question: Some popular sites do say the incorrect answer, and it's reasonable to not be sure that dictionary.com is not a reliable scientific source. – user191954 Sep 2 '18 at 10:54
• @Chair there are 4 mentions of -273.15°C on the dictionary.com page for absolute zero, and only one for -273.16°C. Otherwise a simple google search yields the answer, as I wrote. Or a visit to Wikipedia, etc. – thermomagnetic condensed boson Sep 2 '18 at 11:31
• @Chair Google displays the content of Dictionary.com, there is no need to click on the link itself, and the result displayed is the correct one. – thermomagnetic condensed boson Sep 2 '18 at 12:05
• @user54826 You can cast a close vote/flag if you believe the prior research is poor enough (I don't think it is too bad a question). We disagree about the prevalence of incorrect resources and that's how it goes; though your case is not without justification. Maybe 5 users with 3k rep will vote to close this, I wouldn't be surprised if that happens. But arguing over minutiae is pointless. – user191954 Sep 2 '18 at 12:11

The kelvin, unit of thermodynamic temperature, is the fraction $\frac{1}{273.16}$ of the thermodynamic temperature of the triple point of water.
Hence the triple point of water is $273.16\ \rm K$. Comparing to the $0.01\ \rm °C$ reference (i.e. $273.16\ \mathrm{K}$ is the same as $0.01\ \mathrm{°C}$), we see that absolute zero is $-273.15\ °\rm C$.