BB/100 is short for "big bets per hundred hands" and is a measurement of how much money a player is making at poker. Knowing their BB/100 is a key part to proper bankroll management. On a long-term average this is likely the most factual indicator of a player's overall performance.

A big bet is simply two times the big blind, or two times the minimum bet for a game. Thus to earn 4BB/100 at a $1 no-limit table would mean to earn $8 per 100 hands.

It is generally used for money play, but can be equally well calculated for tournament play if several tournaments are averaged together. This allows a single unified view of the performance of a particular player.

Expectations

How much a player makes can vary greatly depending on the games they are playing, the quality of the player, the strategy they are using, and the particular string of luck they are having. What is a good BB/100 rate and what is bad is not a fixed rule. Though anything negative is obviously bad, as it indicates a loss of money.

In general a player with a rate of 1-3 is doing well, 4-7 is doing very well, and 8 or more is having a very good streak. Some people will indicate that the numbers could be higher in no limits, but only by a small amount, say 1-3.

It is also possible a player could increase their rate by going down a level and playing against easier opponents. Similarly a player with a high rate can usually go up a level, accept a small drop in their rate, but see an overall increase in their earnings. This however generally assumes that increased rates have better players, which is in general true, the pattern is somewhat uncertain at lower limits.