[pzhon]

Yes, you can compute your current comfort level by

comfort = bankroll * true win rate / (standard deviation^2).

As you note, everything on the right hand side should be expressed in the same units. You can convert everything to $, or to big blinds, or to buy-ins.

The comfort level of 31 looks like you are being quite conservative, so you might be looking at the possibility of moving up when you get more data on your win rate. However, it's natural to go above your target comfort level since the stake levels are discrete (there is no NL $17 to try en route to NL $25) and the games get tougher as you move up.

If your win rate at NL $25 expressed in $/100 is lower than your win rate at NL $10, then in the short run, it is better to play NL $10 regardless of your bankroll. You might still take shots at NL $25 with the hope that your win rate will improve, or that you will more rapidly gain the skills to beat higher levels while playing NL $25 than NL $10.

To determine when moving up is justified in the short run, you can compute the comfort level of the difference between the two levels,

differential comfort = bankroll * difference in win rates / (difference in variances)

For example, suppose you win $10/100 with a standard deviation of $80/100 at NL $100, and $15/100 with a standard deviation of $180/100 at NL $200, and suppose your bankroll is $5000. The difference in win rates is ($15-$10)/100 = $5/100, and the difference in variances is $180^2 - $80^2 = 26000 square dollars per 100 hands. Your differential comfort level is 5 * 5000 / 26000 ~ 0.96. Generally, you should move up if the differential comfort level is more than half of your target comfort level, so if your target level is 2 or greater, this says you should stick to NL $100 at the moment. This may be the case even though your comfort level at NL $200 would be 5000 * 15 / 180^2 ~ 2.3 which might be slightly greater than your target comfort level, and you would much rather play NL $200 than nothing.