Basketball Offensive Rating Calculator (ORtg)

Background.

Offensive rating is how basketball answers the question that points per game cannot: is this a good offence, or just a fast one? A team that plays at 105 possessions per 48 minutes will score more points than one playing at 95 even if it is worse at scoring. Dividing points by possessions and multiplying by 100 removes tempo entirely and leaves efficiency, which is why every serious evaluation of an NBA team since Dean Oliver's Basketball on Paper has been conducted in these units.

The formula is ORtg = 100 x PTS / Poss, exactly as NBA.com's official glossary gives it. This calculator returns that, plus defensive rating (100 x opponent points / possessions), net rating (the difference between the two), and both figures restated as points per possession. In the 2023-24 NBA the league average offensive rating was 115.3 — meaning an average possession produced 1.153 points — while the champion Boston Celtics led at 123.2 and the Denver Nuggets, used as the worked example here, posted 118.5 offensively and 113.0 defensively for a net rating of +5.4.

Net rating deserves special attention because it is, empirically, the single most predictive team statistic in the sport. It is point differential per 100 possessions, and it correlates with future winning far better than actual win-loss record does, largely because it is not distorted by close-game luck. As a rough scale: 0.0 is exactly average, +2 is a playoff team, +5 is a contender, +8 is a title favourite, and anything at or above +10 over a full season puts a team in historical company — Boston's +11.6 in 2023-24 is a recent example.

One design decision on this page needs stating plainly. Possessions are an input here, not something the calculator estimates for you. That is deliberate. NBA.com publishes a possession count for every team, so most users already have the number; and estimating possessions from a box score is a substantial calculation in its own right, which the pace factor calculator on this site exists to perform. Enter your box-score totals there, take the possession figure it produces, and bring it back here.

A second scope note. Basketball-Reference publishes two different things under the name Offensive Rating: the team version implemented here, and Dean Oliver's individual player version, ORtg = 100 x (PProd / TotPoss). The individual formula requires around twenty intermediate quantities — scoring possessions, assisted-basket weights, offensive rebound weights, team play percentage and more — and cannot be reduced to a short expression. This page implements the team rating only and does not offer an approximation of the individual one, because a simplified individual ORtg presented as ORtg would not be ORtg.

What is offensive rating calculator?

Offensive rating, abbreviated ORtg or OFFRTG, measures points scored per 100 possessions. NBA.com's official glossary defines it as 'a team's points scored per 100 possessions' with the formula 100 x Points / POSS, and Basketball-Reference credits its development to Dean Oliver, author of Basketball on Paper. Its defensive counterpart, DRtg, is points allowed per 100 possessions, computed with the same possession count on the reasoning that both teams in a game get essentially the same number of possessions — they alternate, and the count can differ by at most one. Net rating is simply ORtg minus DRtg, giving point differential per 100 possessions. The reason the statistic is expressed per 100 possessions rather than per game is that possessions, not minutes, are the fundamental unit of opportunity in basketball: two teams playing a 48-minute game may use 92 or 105 possessions depending on how fast they play, and comparing their raw point totals confuses tempo with quality. Dividing by possessions removes tempo completely. The scale is set at 100 possessions rather than 1 purely for readability, since a rating of 115.3 is easier to talk about than 1.153 points per possession — the two are the same number. Note that Basketball-Reference also publishes an individual player offensive rating, based on Dean Oliver's much longer points-produced-per-individual-possession framework; that is a different statistic despite the shared name, and it is not what this page computes.

How to use this calculator.

1. 01Choose your span — one game, a stretch of games, or a full season — and use it consistently for all three inputs.
2. 02Enter the team's points and the opponents' points for that span.
3. 03Enter possessions. NBA.com publishes POSS for every team on its advanced team pages. If you only have a box score, run the numbers through the pace factor calculator on this site first — it turns field goal attempts, free throw attempts, offensive rebounds and turnovers for both teams into a possession estimate.
4. 04Read the offensive rating against the league context. The 2023-24 NBA average was 115.3, so anything above about 118 was a good offence and above 121 an elite one. Ratings have risen sharply over the last decade, so always compare against the same season's average rather than an absolute standard.
5. 05Read the defensive rating remembering that lower is better. In 2023-24, under 112 was a strong defence and under 110 was elite.
6. 06Use net rating as the headline number when comparing teams. Roughly: 0.0 average, +2 a playoff team, +5 a contender, +8 a title favourite, +10 or above historically dominant.
7. 07For a single game, be aware that ratings are extremely noisy — a 130 offensive rating in one game says little about a team. The statistic stabilises over roughly twenty games.

The formula.

The calculation itself is a single division: ORtg = 100 x PTS / Poss. Everything interesting is in why possessions are the right denominator and where the possession count comes from.

Why possessions and not minutes. A basketball possession begins when a team gains control of the ball and ends when it scores, turns the ball over, or misses a shot that the defence rebounds. Two teams playing the same 48 minutes may use very different numbers of them — in 2023-24 Indiana used 101.7 per 48 minutes and Denver 96.8. Points per game therefore conflates two independent things: how many chances a team gets, and how well it uses them. Points per possession separates them, and pace measures the other half. This is the foundational insight of Dean Oliver's Basketball on Paper and the reason essentially all modern team evaluation is conducted in per-100-possession units.

Why defensive rating uses the same possession count. Possessions alternate, so over any game the two teams' counts differ by at most one, and over a season the difference is negligible. Using a single figure for both is therefore both standard and accurate. That also means net rating has a clean interpretation: it is exactly point differential divided by possessions, times 100.

Where the possession count comes from. NBA.com publishes POSS directly. If you are working from a box score, the standard estimator published by Basketball-Reference averages a team-side and an opponent-side estimate: Poss = 0.5 x ((Tm FGA + 0.4 x Tm FTA - 1.07 x (Tm ORB / (Tm ORB + Opp DRB)) x (Tm FGA - Tm FG) + Tm TOV) + (Opp FGA + 0.4 x Opp FTA - 1.07 x (Opp ORB / (Opp ORB + Tm DRB)) x (Opp FGA - Opp FG) + Opp TOV)). That is exactly what the pace factor calculator on this site computes, so the intended workflow is to estimate possessions there and bring the number here.

A note on rounding. Basketball-Reference publishes offensive and defensive ratings to one decimal place and then prints net rating as the difference of those already-rounded figures. For Denver in 2023-24 that gives 118.5 - 113.0 = +5.5, whereas the unrounded difference is 5.42. This calculator reports the unrounded value. Neither is wrong; they are the same quantity rounded at different points, and the discrepancy is never more than 0.1.

What this page does not compute. Dean Oliver's individual player offensive rating shares the name but is a completely different calculation: ORtg = 100 x (PProd / TotPoss), where individual total possessions decompose into scoring possessions, missed field goal possessions, missed free throw possessions and turnovers, and scoring possessions themselves require an assisted-basket weight, a team offensive rebound weight and a team play percentage. It needs full team and opponent totals and roughly twenty intermediate steps. Approximating it would produce a number that is not ORtg, so this page implements the team rating only and says so.

A worked example.

Frequently asked questions.

References& sources.

1. [1]NBA.com official Stats Glossary, entries 'Offensive Rating' ("Measures a team's points scored per 100 possessions ... Formula 100*((Points)/(POSS)"), 'Defensive Rating' ("The number of points allowed per 100 possessions by a team ... Formula 100*((Opp Points)...") and 'Net Rating' ("Measures a team's point differential per 100 possessions ... Formula OFFRTG - DEFRTG").
2. [2]Basketball-Reference.com Glossary, entry 'ORtg': "Offensive Rating (available since the 1977-78 season in the NBA); for players it is points produced per 100 possessions, while for teams it is points scored per 100 possessions. This rating was developed by Dean Oliver, author of Basketball on Paper." Also the DRtg entry and the team possession formula quoted in the explanation.
3. [3]Basketball-Reference.com, 'Calculating Individual Offensive and Defensive Ratings' — the full Dean Oliver individual framework (ScPoss, qAST, Team_ORB_Weight, Team_Play%, PProd and the rest) that this page deliberately does not approximate, plus the team-level definition Team_Defensive_Rating = 100 * (Opponent_PTS / Team_Possessions).
4. [4]Basketball-Reference.com, 2023-24 NBA season summary — Denver Nuggets points (9418) and opponent points (8987) used in the worked example with published off_rtg 118.5, def_rtg 113.0 and net_rtg +5.5; the league-average rating of 115.3; Boston's league-leading 123.2 offensive and +11.6 net rating; and the Indiana and Denver pace figures quoted.
5. [5]Oliver, D. (2004). Basketball on Paper: Rules and Tools for Performance Analysis. Potomac Books. The origin of possession-based efficiency ratings and of the argument that points per possession, not points per game, is the correct unit for evaluating basketball offence and defence.