Bankroll calculator
Your bankroll is the money set aside for poker. This tells you the biggest game it can stand, the point at which to move down, and the point at which you can move up.
Based on 30 buy-ins. A cash game buy-in is 100 big blinds.
How the figure is worked out
The bankroll is divided by the number of buy-ins you want to keep. For cash games a buy-in is 100 big blinds, so a bankroll of $500 with 30 buy-ins allows a buy-in of $16.67, which is a big blind of about 17 cents, and the stake at or below that is $0.05/$0.10. The move-down point is 20 buy-ins at that stake, $200, and the move-up point is 30 buy-ins at the next stake, $0.10/$0.25, which is $750.
For tournaments the bankroll is divided by 100 or 200. The regular buy-in shown is half the ceiling, because playing the biggest buy-in you can afford every time leaves no room for a normal losing stretch, and in tournaments the losing stretches are long.
These are rules of thumb that fit a player who is winning a little. A player who is losing needs no bankroll rule, because no bankroll lasts; a player winning a lot can play more aggressively. The variance calculator shows the swing behind the rule for your own win rate.
Questions
How many buy-ins do I need for cash games?
30 buy-ins of 100 big blinds is the usual figure for a winning player, 50 if you want the swings to feel smaller or you are not yet sure you are winning. At $0.05/$0.10 a buy-in is $10, so 30 buy-ins is $300.
How many buy-ins do I need for tournaments?
100 or more, because most tournaments pay nothing and a good player's profit comes from a few deep runs. For large fields or fast structures, 200.
When should I move down?
When you fall to about 20 buy-ins for the stake you are playing. Moving down early is cheap; going broke is not. Move back up when the bankroll again covers the full number of buy-ins for the higher stake.
Does rakeback change this?
It lowers the swings a little, because part of your result arrives whether you win or lose at the table, but it does not change the buy-in rule. Treat it as a bonus on top.