NBA Restricted Area Rule: What the Four-Foot Arc Does
The NBA restricted area rule explained: why a help defender inside the four-foot arc cannot draw a charge, the lower box exception and how replay judges it.
By CricketTaken EditorialPublished NBA Rules22 min read
- Arc radius
- 4 feet
- Measured from
- Center of the basket ring
- Introduced by the NBA
- 1997-98
- Applies to
- Secondary defenders
Draw a semicircle four feet from the center of the rim. Any help defender who plants himself inside it to take a charge on a player driving to the basket gets nothing: the NBA's restricted area rule says contact with him is not a charge, so the official calls a blocking foul on the defense. That is the whole purpose of the painted arc under each basket, which the league added for the 1997-98 season.
The NBA's comments on the rules put it in one line: an offensive foul should not be called for charging if the contact is with a secondary defensive player who has established a defensive position within the restricted area for the purpose of drawing an offensive foul. The arc does not bind the man guarding the ball, it does not protect a player who caught the ball close to the basket, and it does not excuse an offensive player who leads with his knee. Each of those limits is covered below, along with the measurements, the replay review and how the college, WNBA, FIBA and high school rulebooks compare.
A help defender inside the arc cannot draw a charge
Consider a drive from the right wing. The ball handler beats his man off the dribble and heads for the rim. A teammate of the beaten defender, the help-side big man, slides across from the weak side and stops directly under the basket, square to the driver. The driver runs into him and both go down. Outside the arc, that is a textbook charge if the help defender got there before the driver began his upward motion. Inside the arc, it is a block. The defender's timing and posture no longer matter.
That reversal is the rule's entire effect. It does not create a new kind of foul or a violation. It removes one route to an offensive foul, the help defender's charge, from a small area directly under the basket, and leaves everything else in the block-charge decision as it was. A help defender who wants to stop a driver inside the arc can still contest the shot, block it cleanly or stand straight up. What he cannot do is take the hit and expect a whistle in his favor.
What the rule is protecting
The arc protects the driver's path to the rim. Before it existed, defenders had a simple, low-effort option against a strong penetrator: get under the basket, plant, and wait. The driver either pulled up, passed, or ran into a defender who had all the rights of a legally established position. That made attacking the basket a gamble, and it rewarded a defense that made no attempt to block the shot or steal the ball. The restricted area turned the space right under the rim from a trap into a lane.
How that space affects the broader charge-or-block decision, including the timing deadline that applies everywhere else on the floor, is set out in our guide to the NBA charge vs block call. This page concentrates on the arc itself.
Four feet from the rim: the measurements of the restricted area arc
The rulebook defines the restricted area as the area bounded by an arc with a four-foot radius measured from the center of the basket ring. That point is not on the floor; it is ten feet up. The arc on the floor is the projection of it, a half circle eight feet across centered on the spot directly below the middle of the rim. The rulebook then runs the two-inch line straight back from each end of the half circle, parallel to the lane lines, to the face of the backboard.
Where that half circle sits follows from the standard court. The face of the backboard is four feet inside the baseline. The inside of the rim is six inches from the backboard and the ring is 18 inches across, so the center of the ring is 15 inches in front of the backboard, or 5 feet 3 inches from the baseline. Add the four-foot radius and the front of the arc reaches about 9 feet 3 inches from the baseline, well short of the free-throw line at 19 feet.
| Court marking | Distance from the baseline | What it marks |
|---|---|---|
| Face of the backboard | 4 feet | The plane behind which the arc no longer matters |
| Center of the basket ring | 5 feet 3 inches | The point the four-foot radius is measured from |
| Front edge of the restricted area arc | About 9 feet 3 inches | The outer limit of the no-charge zone |
| Top of the lower defensive box | 13 feet | The bottom tip of the free-throw circle |
| Free-throw line | 19 feet | 15 feet from the face of the backboard |
Across the floor, the 16-foot lane leaves four feet between each side of the arc and the lane line. The arc therefore covers the central half of the lane's width close to the rim, and almost nothing else. A defender standing at the block, the low post marks along the lane line, is well outside it.
Why four feet
Four feet is about one long stride for an NBA player. A defender who sets up just outside the arc has left the driver a stride of open floor before the rim, enough to finish or pull up without running through him. A defender inside it is effectively standing where the driver must go to lay the ball in. The number was a judgment about where a help defender stops defending and starts obstructing. FIBA's equivalent, set in metric, is 1.25 meters, almost exactly the same distance.
Primary and secondary defenders: who the arc binds
The rule applies to secondary defenders only, and that limit is easy to miss.
A primary defender is the player guarding the ball handler. If he has stayed in front of the dribbler all the way from the perimeter to the basket, he did not arrive late; he has been in the path the whole time. Pushing him back inside the arc does not strip his rights. If the driver lowers his shoulder and runs over him under the rim, the official judges the play by the ordinary charge-block tests, and a charge is available.
A secondary defender is everyone else: the help defender who leaves his own man to stop the drive. He is the player the rule was written for, because he is the one who can camp under the basket in advance and wait. The arc says that if he wants to stop the drive by taking a charge, he must do it from outside the four feet.
When the primary defender becomes secondary
The distinction is not always clean. A defender who gets beaten, falls a step behind and then recovers in front of the driver near the basket may be treated as having lost his primary status, depending on the official's view of the play. The same is true on switches and double-teams. The rulebook's language turns on whether the defender established position under the basket for the purpose of drawing the foul, and help that arrives from the side late in a drive is exactly that. Officials make that call quickly and not always consistently.
The center who was already standing there
A harder case is the help defender who did not rotate at all. A center guarding an opponent parked in the dunker spot, just off the block, may be standing near the rim before the drive even starts. When the driver comes, he shifts a foot to his left and the driver runs into him inside the arc. He did not race across the floor to set up. He was guarding his own man.
The rule still treats him as a secondary defender, because he is not guarding the ball. What protects the driver is the location, not the defender's intent, and a big man who wants to stop the drive by drawing a charge has to step up and meet it outside the arc, leaving his own man behind him. That is the trade the rule forces on every interior defender. Staying home under the rim keeps the dunker covered and gives up the charge. Stepping up to the edge of the arc makes the charge available and leaves a lob or a dump-off pass open. Coaches spend a good deal of film time on which of those a given center should choose against a given driver, and the answer usually depends on how well the driver passes.
On the line or over it: how position inside the arc is judged
The test is the defender's feet, and the standard is strict. The NBA's video rulebook states that a secondary defensive player must have both feet established completely outside the restricted area line to draw an offensive foul.
Three consequences follow. A defender with one foot clearly outside and one foot inside the arc is in the restricted area. A defender with a foot touching the painted line is in the restricted area, because "completely outside" leaves no room for the line. And a defender whose toes are outside but whose heels are raised above the line, hanging over it without touching the floor inside, is also in the restricted area. The NBA has published video of exactly that last play, ruled a blocking foul because the help defender's heels were raised above the arc.
The heel rule matters because defenders preparing to take a hit often rise onto their toes and lean back. A player who sets up with his heels just over the arc can look as if he is outside it in real time. On replay, the overhang is visible, and the call is a block.
The moment that counts
Two moments count. The video rulebook's standard has the secondary defender establish both feet completely outside the line, and establish that position before the offensive player starts his upward shooting motion. The heels-raised ruling shows the position also has to hold when the contact comes: the defender in that clip began with both feet on the line and lifted his heels over it as the driver hit him. A help defender who plants on the paint is inside from the start, and one who rocks back over the line at the moment of impact has given the position away.
- Primary or secondary defender?The rule binds only the help defender. A primary defender who stayed in front of the ball uses the normal tests.
- Where did the play start?If the offensive player caught the ball inside the lower defensive box, the arc does not apply.
- Going to the rim?A driver moving behind the backboard or away from the basket is not covered by the arc.
- How did the offense make contact?Leading with a knee or foot, or clearing with the off arm, is an offensive foul wherever the defender stands.
- Where are both feet?Both feet must be completely outside the arc line; on the line or heels raised over it counts as inside.
- RulingHelp defender inside the arc and no exception applies: blocking foul. Otherwise: judge the play as a normal charge or block.
The order of questions under the NBA's restricted-area rule for a contact play on a drive. If any answer takes the play outside the rule, officials fall back to the ordinary charge-block tests.
The lower defensive box exception
The arc stops protecting the offensive player when the play starts close to the basket. The NBA's exception reads: any player may be legally positioned within the restricted area if the offensive player receives the ball within the lower defensive box.
The lower defensive box is the area between the three-foot posted-up marks, the bottom tip of the free-throw circle and the endline. The posted-up marks are the hash marks three feet outside each lane line on the baseline; the bottom tip of the circle is six feet below the free-throw line. On a standard court that makes the box about 22 feet wide and 13 feet deep, the area most people would call the low post and the paint below the circle.
The logic of the exception is that the arc was meant to protect drivers who attack the basket from outside, coming at speed, from defenders who were waiting for them. A post player who catches the ball on the block, or a cutter who receives a pass two feet from the rim, is not a driver arriving from distance. The help defenders around him were already there, guarding the paint, not camping in anticipation of a drive. So the arc goes away and the ordinary rules apply: a defender who established legal position first can draw a charge even inside four feet.
Dribbling out and back in
The exception is triggered by where the ball is received, not by where the contact happens. A player who catches in the lower defensive box and immediately attacks the rim gives up the arc's protection. The NBA's video rulebook includes a charge called inside the restricted area on a player who gained a new possession in the lower defensive box. A player who catches on the wing, outside the box, and then drives inside it is still protected.
Drives that are not going to the rim
The arc also does not cover a player who is not heading directly to the basket. The NBA's video rulebook shows a play in which Anthony Davis established position in the path of Mike Scott, who was dribbling behind the backboard rather than toward the rim. The ruling was a charge. Since the offensive player was not going directly to the basket, the restricted area did not apply even if the defender was standing inside it. Baseline drives that carry under and past the rim, rather than up to it, are judged the same way.
Offensive fouls the arc does not excuse
The restricted area protects the driver from a help defender's charge. It does not license him to foul. The NBA's comments state that an offensive foul shall be assessed if the player initiates contact in a non-basketball manner, and give examples: leading with a foot, an unnatural extended knee.
The commonest calls are three.
Leading with the knee or the foot
A driver who lifts his knee into the defender's midsection as he rises, or who swings a leg out, has initiated contact in a way that is not part of a normal shot. The NBA's video rulebook classes this as an offensive foul with the restricted area not applying. The same play outside the arc would be an offensive foul too; the point is that standing inside the arc does not make the defender responsible for being kneed.
Clearing out with the off arm
A shooter who uses his free arm to ward off the help defender, pushing his chest or his face to create room for the layup, is called for an offensive foul. The league has published video examples of exactly this, including a layup shooter warding off to the face of a contesting defender. Again, the defender's position inside the arc is irrelevant.
Contact that is not a basketball play
The broader category covers drivers who throw their bodies into a defender at an angle, launch sideways, or otherwise go looking for contact instead of the basket. The NBA's officiating emphasis from 2021-22 on non-basketball moves pushed officials toward no-calls or offensive fouls on those plays, and the restricted area offers no shelter for them.
| Play inside the restricted area | Usual NBA ruling |
|---|---|
| Help defender sets up inside the arc and is run over on a drive to the rim | Blocking foul on the defense |
| Help defender with both feet completely outside the arc, in position before the upward motion | Charge on the offense |
| Help defender with his heels raised over the arc line | Blocking foul on the defense |
| Primary defender stays in front of the dribbler all the way to the rim | Judged under the normal charge-block tests |
| Offensive player caught the ball inside the lower defensive box | Arc does not apply; normal tests |
| Driver moving behind the backboard rather than to the rim | Arc does not apply; normal tests |
| Shooter leads with a knee or wards off with his arm | Offensive foul |
Verticality inside the restricted area
A help defender inside the arc is not obliged to get out of the way. He may contest the shot. What he cannot do is take a charge.
The NBA's verticality principle gives every player the right to the space directly above him, including jumping straight up with his arms raised. A secondary defender in the restricted area keeps that right. If he jumps straight up and the shooter jumps into him, the contact is not automatically a block.
The video rulebook adds a requirement that catches out lazy help defenders. In a ruling on a play inside the restricted area, the league explained that the secondary defender had jumped vertically but had not made an active attempt to defend the shot, and called a blocking foul. To be protected by verticality inside the arc, a help defender has to do two things: jump vertically, and actually try to block or contest the shot. Jumping straight up with his arms down, or turning away as he rises, is just a different way of taking the hit, and the arc forbids taking the hit.
The verticality era
That distinction shaped a style of rim protection. Through the early 2010s, the Indiana Pacers' Roy Hibbert became the best-known exponent of meeting drivers with arms raised straight up, staying vertical and letting the shooter come to him. Commentators started using the word verticality in broadcasts, and coaches across the league taught it. The appeal was that a defender who could not legally take a charge under the rim could still be a wall. The risk was that any drift forward, or any arm coming down, turned the wall into a foul.
How the restricted-area call is reviewed in the final two minutes
The arc is the part of the block-charge call that video can settle cleanly. Feet are either inside a painted line or not. That is why the NBA built a specific replay trigger around it.
In the last two minutes of the fourth period and the last two minutes of any overtime, officials may trigger an instant replay review when they have determined that illegal contact occurred on a block-charge play but are not reasonably certain whether the defender was inside or outside the restricted area. The replay center official then reviews the play. The rule lets the review decide whether the defender was inside or outside the restricted area and whether he was in a legal guarding position, and it may also pick up an unsportsmanlike act or a flop on the same play.
The review does not reopen whether there was a foul at all. The officials must already have decided that illegal contact occurred. Replay decides which way it goes. Outside the last two minutes, this trigger does not exist, and a crew that wants a second look at the arc on a play in the second quarter cannot initiate one on its own.
Coach's challenges on arc plays
At any point in the game, including the final two minutes, a coach may use a challenge on a called personal foul against his team, which includes a block called on his help defender or a charge called on his ball handler. Each team has one challenge per game, with a second awarded if the first succeeds, and each challenge requires a timeout. Restricted-area plays are among the most attractive to challenge, because the foot-on-the-line question is visible in slow motion in a way timing questions often are not. The broader rules on what the replay center may review are covered in the site's explainer on NBA replay review rules.
What the arc changed for help defense
The arc did not end the charge. It moved it.
Help defenders now try to meet drivers earlier, a step or two outside the restricted area, often around the edge of the lower defensive box. That is a harder play to make. The help defender has to read the drive sooner, leave his own man sooner and arrive before the driver begins his upward motion, rather than waiting under the rim for the driver to come to him. A help rotation that gets there late from the weak side is now a block twice over: late for the timing rule and inside the arc.
The other answer was to stop trying to draw charges at the rim and contest instead. The modern rim protector is judged by how many shots he alters near the basket, and the shot-tracking statistics described below were built partly to measure that. Big men who can jump straight up and challenge without fouling became more valuable once standing still under the rim stopped being a reliable defensive play.
The sliding-under problem
The arc also helped with the play that worried the league most: a help defender sliding under an airborne shooter in the last instant. Under the timing rule, that is already a block when the defender arrives after the upward motion began. Inside the arc, it is a block even if the official thinks the defender got there first. The two rules together sharply reduced the incentive to slide under a player in the air, which is the play most likely to send someone crashing to the floor. Defensive schemes built around protecting the paint are described in the site's guide to help defense in basketball, and the rule that limits how long a defender may camp in the lane at all is explained in our guide to the NBA defensive three-second violation.
The restricted area as a shot-chart zone
The arc has a second life in the box score. The NBA's statistics site divides the court into shot zones, and the closest of them is called the Restricted Area. The others are In the Paint (Non-RA), Mid-Range, Left Corner 3, Right Corner 3, Above the Break 3 and Backcourt. Shots taken from inside the painted arc are logged in the first zone.
That classification has nothing to do with the charging rule. The league borrowed the arc because it was already painted on every court and made a natural boundary for shots at the rim: layups, dunks, tip-ins and very short putbacks. It is the zone where shooting percentages are highest, and it serves as a convenient definition of a shot at the rim in a way a vague phrase like "close range" cannot.
When analysts talk about a team's rim attempts or a defense's rim protection, they are often working from restricted-area numbers: how many shots a team takes there, how often it scores, and how a defender's presence near the arc changes opponents' accuracy. Player tracking data, which records where every player is on the floor many times per second, has made that measurement more precise. The site's explainer on NBA tracking data describes how those figures are gathered.
A note on reading the numbers
Because the arc is small, small differences in shot location move shots between zones. A layup taken from just outside the arc, on a drive that stopped a step short, is filed as an In the Paint (Non-RA) attempt. The zone is a useful category, not a perfect description of shot difficulty.
The arc in college, the WNBA, FIBA and high school
The restricted area spread from the NBA to other rulebooks slowly, and not everywhere.
College basketball adopted it in stages. The NCAA men's game introduced a three-foot arc for the 2011-12 season and widened it to four feet for 2015-16, matching the NBA's radius. As in the NBA, the arc binds secondary defenders. Women's college basketball, played on the same floors, applies an arc under its own rules committee's provisions, and a reader comparing a women's college game with the NBA should check the current NCAA women's rulebook for the detail. Our guide to the gaps between college and NBA rules covers how the two codes differ more broadly.
The WNBA plays on courts marked like the NBA's and applies a restricted area under its own rulebook, which in most respects follows the NBA's guarding and charging principles. Where the leagues differ, our side-by-side of WNBA and NBA rules sets out the detail.
FIBA, the international federation, added the no-charge semicircle in its 2010 rules changes, with a radius of 1.25 meters measured from the point on the floor directly below the center of the basket. That is just over four feet one inch, a fraction larger than the NBA's arc. FIBA's semicircle works the same way: a defender inside it cannot draw a charge from a player penetrating toward the basket, and the semicircle lines are treated as part of the area, so a foot on the line counts as inside. The site's explainer on FIBA rules compared with the NBA covers international play more widely.
High school basketball under the NFHS has no restricted area. The national federation has not adopted one. Some high school games are played in gyms shared with college teams, so an arc may be painted on the floor, but under the NFHS rulebook it has no meaning: a help defender in legal guarding position under the basket can draw a charge on a high school court.
| Rulebook | Arc | Radius | Applies to |
|---|---|---|---|
| NBA | Restricted area, since 1997-98 | 4 feet from the center of the ring | Secondary defenders |
| NCAA men | Restricted area, since 2011-12 | 3 feet at first, 4 feet since 2015-16 | Secondary defenders |
| WNBA | Restricted area | Under WNBA rules | Under WNBA rules |
| FIBA | No-charge semicircle, since 2010 | 1.25 meters from below the ring | Defenders against a penetrating player |
| NFHS high school | None | Not applicable | Not applicable |
Why the NBA drew the arc in 1997
The arc came out of a specific kind of collision. Through the late 1980s and early 1990s, NBA defenses were physical in ways the league later legislated against: hand-checking on the perimeter, heavy bumping of cutters, and big men who held the paint. One of the most effective team defensive tactics was simple. Send the help early, plant a body under the rim and let a driver run into it.
That produced charges. It also produced ugly, dangerous plays: drivers who had already left the floor colliding with defenders who arrived underneath them, landing on their backs and heads, and defenders absorbing hits to the chest at full speed. And it produced a style of defense that, from the league's point of view, did not look like defense. A help defender standing under the rim with his hands down was not trying to block the shot or take the ball. He was trying to induce a foul.
The NBA's answer for the 1997-98 season was to paint a small arc and define it as a place where that particular play stopped working. It did not abolish the charge, which would have handed the floor to the offense, and it did not restrict primary defenders, who earn their position by staying in front of the ball. It singled out the help defender who waits under the rim, the one player in the sequence whose role was to fall down.
What came after
The arc was one piece of a longer process. Hand-checking had already been restricted in the mid-1990s; in the years after the arc, the NBA allowed zone defenses for the 2001-02 season while adding the defensive three-second rule, and tightened hand-checking again for 2004-05. The effect of all those changes was to open the floor for drivers and shooters. The restricted area was the smallest of them, eight feet of painted line under each basket, and it changed how every NBA help defender has played since. For the history of the perimeter rule, see our guide to the NBA hand-checking rule, and for the rest of the sport's rules and explainers, the site's basketball section.