The relationship between Celsius and kelvin is that degrees Kelvin is equal to degrees Celsius + 273.15. That means that the freezing point of water (0°C) is 273.15° kelvin. This makes an additive relationship between the two quantities, so quantities such as the boiling point and freezing point of water are the same distance apart on the Kelvin scale (100 degrees). This means that kelvin has the same magnitude as Celsius.