The term ROI is an acronym that stands for Return on Investment. Poker players use this to calculate their profitability in tournaments and measure their overall success.
For example, let’s say you played an MTT with a buy-in of $50. You survived the bubble but then lost a coin flip, so you finished in the money and won $120. To calculate your ROI, you have to divide the profit you made from the buy-in amount and multiply it by 100. In this case, it would be calculated as 70/50*100, meaning that your ROI in this tournament was 140%.
Of course, to get an accurate number for your return on investment stat, you need to play many tournaments and take the average out of it. The more you play, the more precise the number becomes.