Sports & Gaming · Statistics · Descriptive Statistics
Defensive Rating Calculator
Calculate a basketball player's Defensive Rating (points allowed per 100 possessions) using box score and possession data.
Calculator
Formula
DRtg = Defensive Rating. Points Allowed = total points allowed while the player was on the court. Possessions = total defensive possessions. Multiplying by 100 normalises the figure to a per-100-possessions rate, enabling fair comparison across players and teams with different playing times.
Source: Dean Oliver, 'Basketball on Paper', 2004. Popularised by Basketball-Reference.com.
How it works
The core formula divides total points allowed by defensive possessions, then multiplies by 100 to normalise to a per-100-possession rate: DRtg = (Points Allowed / Defensive Possessions) × 100. Because it is pace-adjusted, a player who guards 80 possessions and allows 80 points earns the same DRtg (100) as one who guards 40 possessions and allows 40 points.
Player-level defensive rating is harder to calculate than team rating because official box scores do not directly record which points were scored against a specific defender. The blended approach used here weights the player's individual rate by their share of team minutes, and the team rate by the remaining share, producing an estimate consistent with Basketball-Reference methodology.
Analysts use DRtg to compare defenders across eras, team contexts, and playing styles. It appears in lineup analysis, player valuation models (e.g. BPM, RPM), and contract negotiations. Typical NBA values range from about 105 (excellent) to 115+ (poor), with league average varying by season.
Worked example
Scenario: A center plays 32 of the team's 240 total minutes. While he is on court, his team allows 105 points over 100 possessions. The full team allows 108 points over 102 possessions for the game.
Step 1 — Individual DRtg: 105 ÷ 100 × 100 = 105.0
Step 2 — Team DRtg: 108 ÷ 102 × 100 ≈ 105.9
Step 3 — Player minute share: 32 ÷ 240 ≈ 0.133 (13.3%)
Step 4 — Blended DRtg: (0.133 × 105.0) + (0.867 × 105.9) ≈ 13.97 + 91.83 ≈ 105.8
The blended rating of 105.8 is slightly above the individual figure because the team was marginally worse when he was off the court, diluting his personal contribution.
Limitations & notes
Individual Defensive Rating is an estimate. Box scores record steals, blocks, and defensive rebounds but do not log which defender was beaten on any given possession, so all player-level DRtg figures carry uncertainty. Factors like defensive scheme, help defence quality, and opponent shooting luck can inflate or deflate the number. A single game sample is highly volatile; analysts typically aggregate at least 500 possessions before drawing conclusions. This calculator assumes the user supplies possession counts derived from league or tracking data — rough estimates based on field-goal attempts will introduce additional error.
Frequently asked questions
What is a good Defensive Rating in the NBA?
In recent NBA seasons, a team DRtg below 110 is considered excellent, while a DRtg above 115 is poor. League average sits around 112–114 depending on the season. For individual players, context matters enormously — a 108 DRtg on a bad defensive team can reflect better personal defence than a 106 DRtg on a strong team.
How is a defensive possession counted?
A defensive possession ends when the defending team secures the ball — via a defensive rebound, a steal, the opponent making a field goal or free throw, or a turnover. Most modern tracking systems also account for team rebounds and end-of-period possessions. Using field-goal attempts plus 0.44 × free-throw attempts plus turnovers minus offensive rebounds is a common approximation when tracking data is unavailable.
Why do I need team minutes and team possessions?
Player-level box scores do not show which specific points were scored against a defender. The blended model compensates by weighting the player's on-court rate against the team's overall rate, scaled by their share of total minutes. Providing both player and team figures gives a more reliable estimate than using individual data alone.
How does Defensive Rating differ from Defensive Win Shares?
Defensive Rating measures the rate of points allowed per 100 possessions — it is a pure efficiency metric. Defensive Win Shares additionally accounts for the number of possessions played and attempts to translate that efficiency into an estimate of wins contributed. DRtg is easier to interpret in isolation; DWS provides cumulative value over a season.
Can Defensive Rating be used for college basketball or other leagues?
Yes. The formula is league-agnostic — you only need points allowed and possession counts. League-average DRtg differs (college pace and officiating tend to produce higher scoring rates), so never compare a college DRtg directly to an NBA DRtg. Always benchmark against the league average of the specific competition you are analysing.
Does a lower or higher Defensive Rating mean better defence?
Lower is better. Defensive Rating measures how many points a team or player allows per 100 possessions, so a DRtg of 105 means only 105 points were allowed per 100 possessions — better than a DRtg of 112. Think of it like a golf score: you want the number as small as possible.
Last updated: 2025-01-30 · Formula verified against primary sources.