# Kelvin and Celsius

My teachers (also the internet) tells me that Kelvin can never be negative. But when I converted $$-275^\circ$$C to Kelvin, it becomes $$-1.85\,\rm K$$. So, why everyone says that Kelvin can never be negative?

• May 4, 2021 at 13:54

• They tell you correctly that a Kelvin value can't be negative, $$T>0 \,\mathrm K$$.
• Also, they should have told you that a degrees Celsius value can't be below $$T>-273.15 \,^\circ\mathrm C$$.
Sure, you can make up a number below this value, such as $$-275\,^\circ \mathrm C$$. Just like you can make up a number such as $$-10\,\mathrm K$$. These numbers just don't represent reality. A lower temperature limit is a feature of the world we live in. The above two values for the lower limit are identical - called absolute zero - just given in different unit systems.