RFI: Raised First In

When no one has entered the pot yet before the flop, RFI is the percent of the time that a player raises (i.e, an open-raise). Based on the RFI, you can estimate the player's range when they open-raised. For example, if their RFI from the Cutoff is 35%, then you can deduce that when they open-raise they have one of the top 35% of starting hands.

While there's some subjectivity as to what constitutes the “top 35% of starting hands”, there is also has a strong objective component. For example, it certainly includes AJ but not T3. When you have a lot of data on an opponent, you can get a more detailed view using the Player Analyzer.

When you're in the blinds and an opponent raises from late position, check their RFI to see how frequently they open-raise from late position. Some players will try a raise here at almost every opportunity, hoping that you will fold your blinds. You will need to call and re-raise against those players more often or they'll slowly bleed you dry.