Article: Scientists understand the Celsius scale as derived from the Kelvin scale. Though the gaps between Celsius and Kelvin are even larger than the gaps between Celsius and Fahrenheit, one thing that Celsius and Kelvin have in common is that they rise at the same rate. Whereas the ratio for Celsius to Fahrenheit is 1:1.8, the ratio for Celsius to Kelvin  is 1:1. If it seems odd that freezing for Kelvin would be such a high number — 273.15 — it's because the Kelvin scale is based around absolute zero, which is 0K. Though 0°C is the freezing temperature of water, scientists actually understand 0°C as 273.15K. Since the two scales rise at the same rate, then converting Celsius to Kelvin always means simply adding 273.15. For example, if you're working with the temperature 30°C, just add 273.15 to that. 30 + 273.15 = 303.15K. Here's a rough scale so you can test whether your answer makes sense. Note that the Celsius and Kelvin scales increase at the same rate, so the two numbers are always exactly 273.15 apart.  If you start with an integer value of degrees Celsius, your result in kelvins will end in the decimal .15. The lowest possible temperature is -273.15ºC = 0 kelvins. If your result involves negative kelvins, you either made a math mistake or the problem uses impossible values.  ºCelsius kelvins    -100    173.15     -50    223.15     0    273.15     50    323.15     100    373.15     200    473.15     500    773.15

What is a summary?
Understand the scales. Add 273.15 to your Celsius temperature. Check your answer.