On the "leaders" tab, I am ranked 111,990 with 789 points. I can change it to sort by "following" and see that my friend has 122,862 points, but I want to know his overall standing in the ranks.
Go to the leaders tab, change "Filter by" from "Last 30 days" to "Everybody" to see all-time standings. Look at your friend's total points in their profile. At the bottom of the page, type in a random page number (level 29 is at about page 1000). Increase or decrease the page number till you find what page your friend is on. It's a little tedious so you may want to just ask them.