Turnover percentage is defined as, “The percentage of offensive possessions that end in a turnover”. It is considered by many to be a better indicator than the two most commonly used turnover statistics, the total number of turnovers, for comparing opponents in the same game assuming a similar number of possessions, and assist-to-turnover ratios, for comparing individual players. However, these commonly used statistics do not consider pace of the game and do not help you look at comparisons of turnovers on a game to game, team to team, and year to year basis.
Why is this important? Over the course of a season, where a team plays against every other team in the league, larger trends play out, including differences in pace. Turnover percentage or rate allows you to compare, in one season as well as multiple seasons, to other teams in your league, region, or in the country.
Using per-possession turnover stats also allows you to measure the game at its smallest possible unit of measurement that takes both teams in a particular game into account. By normalizing stats to a per-possession basis, we take out the differences in pace of play and in doing so can get closer to crafting real comparisons. A possession in 1999 is the same as a possession in 2019. If you take this one step further and break it down to per-100 possessions, you have a number not a percentage. For example, if a team has a turnover percentage by possession of .194, they have a turnover rate per 100 possessions of 19.4.
The end of a possession is when:
- A field goal is attempted that is not rebounded by the offense. Offensive rebounds are treated as continued possessions, and by subtracting them from the field goal attempts it ensures that both teams have almost the same number of possessions in each game.
- A team commits a turnover.
- A team goes to the free throw line and does not get the ball back. There are some catches here that you need to account for: technical free throws, and 1’s, missed 1 and 1’s, 3 shots, and lane violations. .475 is a good determination that 47.5% of all free throws take up possessions.
- Possession = (FGA-OR) + TO + (.475 X FTA)
- Turnover percentage per possession: TO/(FGA-OR) + TO + (.475 X FTA)
- Turnover Rate per 100 possessions: TO X 100/(FGA-OR) + TO + (.475 X FTA)
Team A has 17 turnovers, 81 field goal attempts, 10 offensive rebounds, and 21 free throw attempts.
17 /71+17+(.475*21) = .175% turnover percentage
100*17 /71+17+(.475*21)+17) = 17.5% turnover rate.
This team turned the ball over about 17 and a half times of every 100 possessions. This is good as an average turnover rate would be around 20.
To help you get started we have created a spreadsheet for team turnover rate per 100 possessions. Feel free to use this however you see fit for your specific team. You could enter the statistics for each game, up to 33. Use every other row for you and your opponents. Or you could use eight rows for the eight teams in the conference. As you enter the relative information in the first four (A-D green labeled) columns the formulas in the last three (E-G red labeled) columns will start to calculate and give you the information you desire.
Using turnover percentage, or rate, for individuals is a bit more complicated because if you wanted to do it by possessions you would have to calculate the number of possessions a player is on the floor. The easiest way to look at the individual percentage is to take the percentage of minutes a player is in the game and divide that into the number of possessions. 20 minutes of play would be ½ of the game or ½ of the possessions. While not 100% accurate, it provides a good baseline for your individual statistics.
Turnovers are like most stats, in that what matters most is the comparison of what you are trying to do on offense and what you are trying to do on defense. During the down time this off season you could insert the season turnover stats for every team in your conference, offensively and defensively, and see how they compare. You could also do the same thing with every game on your schedule. Compare the game to game gaps in turnover rates and see if the gap correlates to wins and losses.
Stay Tuned for the next coaches corner blog – Offensive Rebounding %.