Income percentile for world population

I am trying to calculate the percentile (income brackets) for world population. I have compiled the data from 230 countries; population and GDP per capita. I am stuck and need help calculating the percentile using the population variable as we have built a calculator where people will input in their income on our website and it will output to them where they stand in relation to the rest of the world's income levels. Hope this makes sense. I am a new user and thanks for your help, much appreciated.