Travel score based on the grid cells you’ve selected, three numbers are calculated:
1. The percentage of the world’s countries that you’ve visited
2. The share of the world’s population that lives in these areas
3. The share of the earth’s land surface that lies inside the selected grid cells
The overall travel score is the mean of these three numbers. Of course this calculation method is kind of arbitrary. It’s just my approach to measure how much of the world a person has seen.