Can someone explain player efficiency rating?

[larsk]

I have tried to calculate the PER for some players but i'm having a hard time doing so.
In the formula i found is spoken about leaugestats (lg_FT, lg_PF etc.) but I don't understand what they mean and I haven't found it on the internet yet. If someone could help me it would be great.

Thanks.

[colts18]

league means the league average in those stats. For example, the league average rate of personal fouls per possession. The formula online gives you unadjusted PER. Then the PER is adjusted to a league average of 15.

[larsk]

Thanks!

[fancynapkin]

To be frank, you shouldn't care about it because it is a horrible stat.