📊 Four Factors Calculator
Two box scores in, and the standard answer to why a team won: shooting, turnovers, offensive rebounding and free throws, weighted the way Dean Oliver weighted them.
📊 The Four Factors
| Factor | Weight | Team A | Team B | Edge |
|---|---|---|---|---|
| Shooting (eFG%) (FGM + 0.5 × 3PM) ÷ FGA | 40% | 55.4 | 49.4 | Team A by 6.0 |
| Turnovers (TOV%) TOV ÷ (FGA + 0.44 × FTA + TOV) · lower is better | 25% | 10.6 | 13.2 | Team A by 2.6 |
| Offensive rebounding (ORB%) ORB ÷ (ORB + opponent DRB) | 20% | 19.1 | 23.9 | Team B by 4.8 |
| Free-throw rate (FTA/FGA) FTA ÷ FGA | 15% | 21.7 | 27.3 | Team B by 5.5 |
Team A comes out narrowly ahead on the weighted factors, driven mostly by shooting. A margin this small does not decide a game on its own.
Team B is not far behind, and over a single game these rates are noisy. The Four Factors describe a season far better than they describe an evening.
The weights are Dean Oliver’s estimate of how much each factor matters, from Basketball on Paper. They are not a formula that predicts a score, and the weighted margin above is not a points figure — it explains a result that already happened. A team can win three factors and lose the game.
Four numbers, in order of how much they matter
A box score has forty numbers in it and no opinion about which of them mattered. Dean Oliver’s contribution in Basketball on Paper was to show that four rates account for nearly all of winning — and, more usefully, that they do not matter equally.
Shooting, 40%. Effective field-goal percentage, which credits a made three as half a made shot extra so that a 40% three-point night and a 45% two-point night are measured on the same points-per-attempt scale. It is worth as much as turnovers and rebounding put together.
Turnovers, 25%. Per possession, not per game — a turnover costs you a possession, and possessions are the currency. It is the one factor where a lower number is the better one.
Offensive rebounding, 20%. The share of available offensive rebounds you took. Available is the operative word, and it is why this calculator asks for both teams: the chances that existed are recorded only in the other team’s defensive rebound column.
Free throws, 15%. Attempts per field-goal attempt — how reliably you turn possessions into trips to the line, which is a different skill from making them.
The weights are why this is more useful than a list. Counting factors won will tell you a team that took three of four had the better night, and it will often be wrong, because the one it lost was the one worth 40%. That is the whole point of ranking them.
❓ Frequently Asked Questions
What are basketball's Four Factors?
They are the four things Dean Oliver identified in Basketball on Paper as accounting for nearly all of winning, ranked by how much they matter: shooting at about 40 percent of the explanation, turnovers at 25, offensive rebounding at 20, and getting to the free-throw line at 15. Each is a rate rather than a total, which is what makes them comparable between a fast game and a slow one — a team taking 95 shots and a team taking 80 are not measured on the same scale by raw points, but they are by effective field-goal percentage.
Why do I need both teams' box scores?
Three of the four can be worked out from one line. Offensive rebound rate cannot, and this is the error the metric most often suffers. A rebound is a shared event: the honest denominator is the number of rebounds that were available, and the only record of how many chances existed is the opponent's defensive rebound count. Dividing your offensive rebounds by your own total rebounds gives a number that looks similar and measures something else. This calculator asks for both teams and refuses rather than guessing.
What does effective field-goal percentage do that FG% doesn't?
It stops treating a three-pointer as though it were worth the same as a two. Plain field-goal percentage counts makes and attempts, so a team shooting 40 percent on threes looks worse than one shooting 45 percent on mid-range twos — when the first is scoring 1.20 points per attempt and the second 0.90. eFG% credits each made three as half a made shot extra, which puts both on the same points-per-attempt footing. It is the single most important number in this framework, which is why it carries 40 percent of the weight.
Can a team win three factors and lose the game?
Easily, and that is exactly why the weights exist. Shooting carries as much weight as turnovers and rebounding combined, so losing it badly outweighs winning the other three narrowly. Counting factors won will regularly give you the wrong story. The weighted margin here is a way to keep that straight — but treat it as a description of what happened rather than a score, because that is what it is.
Is the weighted margin a prediction?
No, and it is worth being clear about it. Oliver's 40/25/20/15 is an estimate of relative importance, not a regression that outputs points. Feeding two box scores in gives you a diagnosis of a result that has already happened: which factor decided it, and by how much. Over a season these rates are stable and genuinely predictive of team quality; over a single evening they are noisy, and a game can turn on shot variance or the last two minutes without any of it showing up here.
Why is the free-throw factor about attempts rather than makes?
Because the factor is measuring how well a team generates trips to the line, not how well it shoots once there — free-throw shooting is a separate skill and largely a constant for a given roster. FTA divided by FGA answers the question the factor is asking: for every shot this team takes from the floor, how often does it also get to the line? Some analysts use makes instead of attempts, which folds free-throw accuracy back in; both are in common use, and the version here is the attempts one.