The L/F Ratio or Likes/
Friends Ratio is designed to measure what percentage of your Facebook
friends like your profile picture.
It is obtained by dividing your profile picture's likes by the number of
friends you added, times 100%.
For example: 50 likes, 300 friends -> 50/300 x 100 = 16.7
The L/F ratio is a really handy tool when you want to figure out how many of your Facebook 'friends' are really interested in you! Also, it enables you to compare your ratio to your friends'.
A typical L/F ratio lies somewhere between 3 and 20