Deputy Editor
Online poker legend Phil Galfond has built a poker variance calculator, free for all to use. He announced the tool yesterday on social media.
“I made a variance calculator with many functions I’d never seen in others,” he wrote. “I found ways to show concepts I’ve tried to explain in words, but make much more sense in visual, mathematical outputs.”
Variance is an extremely powerful concept in poker, significantly altering outcomes over even medium-term sample sizes. Using tools such as the one Galfond released can help give players a better grasp of its scope and power.
Galfond has repeatedly credited his long and fruitful career to sound bankroll decisions. While he admits he took many shots above his bankroll, he always maintained that a key factor to survival was his willingness to move down when those shots didn’t go well.
Unfortunately, the tool doesn’t provide anything for tournament players in its current form, even though that format features even greater variance than cash games. Still, for those who play cash, it has a lot to offer.
Galfond’s Poker Variance Calculator Has a Variety of Uses
Galfond’s calculator includes quite a wide range of interesting functions.
To start, players set their measured win rate, standard deviation, sample size, and current bankroll in the top control bar. That provides a baseline on which the tool applies its calculations. Helpfully, if players aren’t sure of these numbers, they can click the “Help Me” button, and a pop-up will guide them through some possible inputs.
Then, players can explore the tabs.
Under “Results,” players can get an idea of their profit probability and risk of ruin across different hand samples. They can also see floor and ceiling results, with some additional possibilities bucketed in between.
The “Downswings” tab lets players see the chances of various levels of loss at some point during a given sample size. For example, a modest live $5-$10 no-limit hold’em winner (+3.5 BB/100) has about a 7% chance of hitting a 25-buy-in downswing over the course of the coming year. A PLO player at the same stakes has around a 27% chance of hitting the same downer, even if they have a win rate that’s twice as large.
Game selection influences variance hugely, in other words.
“Bankroll” helps players budget for their games, using their own risk tolerance and desired aggression level.
Under “Am I a Winner?,” players can plug in observed results, and the calculator estimates the chance that the player is profitable.
Players and backers interested in making a financial arrangement can play around with the numbers under “Backing” and see the expected value of various setups.
Using Five-Year Outlook Hints at the Massive Impact of Variance
Perhaps the most interesting feature of Galfond’s variance calculator is the right-most pair of tabs, “Your Year” and “Zoom Out.” Using these, players can simulate various future outcomes.
Your Year can give players an idea of how their monthly wins and losses might look, which can help with planning budgets. More than anything, it’s a reminder that poker results are going to fluctuate, losing months will happen, and players must keep some money squared away to take care of normal life expenses.
Zoom Out gives a much more fascinating look at the possible divergence that can happen in a poker player’s career due entirely to variance.
For instance, take a $5-$10 live player putting in full-time hours with a very good win rate (+8 BB/100). Simply clicking re-roll over and over shows the wild swings possible for that player. Sometimes, they will become a millionaire. In other sims, they will barely crack six figures in winnings.
The calculator also assumes the player has access to their game consistently and can always move up when bankroll allows. These factors probably aren’t present for most players, further muddying even a winning player’s long-term outlook in poker.
