What is the temperature of absolute zero in degrees Celsius?

The temperature of absolute zero is −273.15°C.

Absolute zero is 0 kelvin, the lowest limit of thermodynamic temperature. The Celsius value follows from the exact relationship between the Celsius and kelvin scales: 0 K equals −273.15°C. It is also −459.67°F.

The idea developed from gas studies. Jacques Charles and Joseph Louis Gay-Lussac found that, under suitable conditions, a gas’s volume or pressure changes predictably with temperature. Extrapolating those relationships suggested a point near −273°C where an ideal gas would reach zero volume or pressure. William Thomson, later Lord Kelvin, proposed an absolute temperature scale in 1848.

Absolute zero cannot be reached by a finite physical process, although laboratories can approach it extremely closely using methods such as laser cooling and evaporative cooling. A common mistake is to treat −273°C as the exact value; −273.15°C is the precise Celsius equivalent.