Bowling (USBC) — Official Rules

Ten-pin bowling is played by rolling a ball down a lane to knock down 10 pins arranged in a triangle at the far end. A game consists of 10 frames. The bowler aims to knock down all pins to maximise pinfall and bonus pins. The player or team with the higher total score at the end of the game (or series of games) wins.

In each of the first nine frames a bowler is entitled to two deliveries (rolls), except that a strike ends the frame after one delivery. A delivery is the rolling of the ball toward the pins. The frame is complete when the bowler has knocked down all pins (strike or spare) or used both deliveries. Players or teams bowl in turn, frame by frame, in a set order.

The 10th frame is special: a bowler who throws a strike or spare earns extra fill ball(s) within the same frame. A strike on the first delivery grants two more deliveries; a spare grants one more delivery; an open frame ends after two deliveries. Thus the 10th frame may contain up to three deliveries, allowing a maximum of 30 pins to be added there.

An open frame is one in which the bowler fails to knock down all 10 pins with the two deliveries of the frame. The score for an open frame is simply the number of pins knocked down (0 to 9), with no bonus. The cumulative game total is the running sum of all frame scores.

A spare is recorded when the bowler knocks down all 10 pins using both deliveries of the frame. A spare scores 10 pins plus the number of pins knocked down on the next single delivery (the first ball of the following frame). It is marked with a diagonal slash on the scorecard.

A strike is recorded when the bowler knocks down all 10 pins with the first delivery of the frame. A strike scores 10 pins plus the pins knocked down on the next two deliveries. Two strikes in a row is a double, three is a turkey, and the first of three consecutive strikes scores 30. It is marked with an X on the scorecard.

The maximum score in a game is 300, achieved by rolling 12 consecutive strikes (one in each of the 10 frames plus the two fill balls of the 10th frame). Each strike, when fully bonused, is worth 30 pins, and 10 frames at 30 equals 300. A 300 game is a perfect game.

For certain televised finals the IBF has used the alternative current-frame (World Bowling) scoring: a strike counts 30 pins regardless of later deliveries, a spare counts 10 plus the first delivery of the same frame, and an open frame counts the pinfall - no fill or bonus balls are carried forward. The maximum game is still 300, reached with 10 consecutive strikes. Traditional cumulative scoring remains the standard method used in most competition and league play.

Pins count as legally downed only when they are knocked over by the ball or by another pin during a legal delivery. Every delivery counts unless a dead ball is declared. Pins knocked down by a legally delivered ball, including pins rebounding from the side or rear cushions and pins toppled by other pins, are counted in the score.

Pinfall is illegal and does not count when: a ball leaves the lane before reaching the pins; a ball rebounds from the rear cushion; pins are knocked down by a ball that has gone into the gutter and returned; pins are downed by the pinsetting (rack) equipment; a pin is touched by a mechanically held or removed pin; or a pin is knocked down while removing a dead wood (downed pins). Pins so downed are respotted to their original positions and do not score.

A foul occurs when a part of the player's body encroaches on or goes beyond the foul line and touches any part of the lane, equipment or building during or after a delivery. The bowling ball is not considered part of the body; crossing the line with the ball alone is not a foul. Fouls are detected by an automatic foul-detecting device or, failing that, by the officials.

When a foul is committed, the delivery counts but scores zero pins - any pins knocked down on that delivery are not credited. The pins are then respotted for the next legal delivery in that frame, if one remains. If a bowler fouls on the first delivery and then clears the remaining pins on the second, the result is a spare (the first ball counting 0). A foul on the second delivery of a frame leaves an open frame scored only on the first ball.

A dead ball is one that does not count and must be re-bowled after the cause is corrected. A delivery is declared a dead ball when: one or more pins were missing or wrongly set before the ball was thrown; a pin is moved or removed before the ball reaches the pins; a wrong bowler delivers, or a bowler delivers on the wrong lane; the bowler is interfered with by another player, spectator, or moving object before the ball reaches the pins; or the pinsetter touches the pins before the ball reaches them. The frame is then bowled again with a full or correct setup.

When a dispute cannot be resolved immediately - for example a protested foul, a count of pinfall, or a legal/illegal pinfall - the bowler shall complete the frame and then bowl a complete provisional frame or ball under protest. Both results are recorded, and the decision of the tournament officials later determines which counts. Protests on a question of fact (pinfall, fouls, lane conditions) must be made before the next delivery.

The lane measures 60 feet (18.29 m) from the foul line to the centre of the head pin (No. 1 pin). Its playing surface is 41.5 inches (1.054 m) wide, made up of 39 boards. A gutter (channel) about 9 to 9.5 inches wide runs along each side of the lane to collect balls that leave the playing surface. The pin deck behind the head pin extends roughly 34 inches to hold the full rack.

The approach behind the foul line shall be not less than 15 feet (4.57 m) in length, free of obstructions, so the bowler can take the run-up and slide before releasing the ball. The foul line is clearly marked across the lane and approach and separates the approach from the playing surface; crossing it with the body during a delivery constitutes a foul (Article 4.1).

Lanes are conditioned with a lane dressing (oil) applied in a defined pattern. The IBF/WTBA prescribes the oil-distribution standards and ratios used for championships, including a minimum amount of conditioner and approved patterns. Bowlers may not alter the lane surface or apply foreign substances. Lane conditions must be uniform and verified before competition.

A bowling ball shall weigh not more than 16 pounds (7.257 kg), with no minimum weight. For a ball of 13 lb or more, the circumference shall be 26.704 in minimum and 27.002 in maximum, and the diameter 8.500 in minimum and 8.595 in maximum (approx. 218 mm). The ball must be made of non-metallic, approved material and be perfectly round when not drilled.

Gripping holes may be drilled for the bowler's fingers and thumb. Balance (weight) holes are prohibited in competition; the only holes permitted are those used for gripping and for the optional single thumb-relief hole. Static imbalance is limited by approved tolerances (top, side and finger/thumb weight). The ball surface must comply with hardness and friction limits and be free of foreign matter.

Ten pins are used. Each regulation pin stands 15 inches (381 mm) tall and weighs not less than 3 lb 6 oz (1.53 kg) and not more than 3 lb 10 oz (1.64 kg); all pins in a set must be within 4 oz of one another. A pin is about 4.75 inches at its widest. Pins are made of approved wood (or wood with plastic coating) of uniform material.

The 10 pins are set in an equilateral triangle of four rows, the head pin (No. 1) nearest the bowler and the back row (Nos. 7, 8, 9, 10) at the rear. Adjacent pin spots are 12 inches (304.8 mm) apart, centre to centre, and each spot is 2.25 inches in diameter. The pins are numbered 1 to 10 from front to back, left to right, for scoring and reporting.

IBF World Championships and major events are contested in Singles (1 player), Doubles (2), Trios (3), Team of Five (5), and All Events (the aggregate of a bowler's scores across the disciplines). In multi-player events each member bowls a full game on a pair of lanes and the team total of pinfall determines placement. Players rotate (move across) lanes after each game to equalise conditions.

In the Baker format, a single game is bowled by the whole team as a unit: each player bowls predetermined frames in rotation so that the five team members together complete one 10-frame game. The IBF uses Baker format for the semifinals and finals of Doubles, Trios and Team events. This format substitutes team rotation for individual completion of a game.

When players or teams finish level on total pinfall for a qualifying position or a medal, the tie is broken by a roll-off (a one-game or one-frame play-off) or by a prescribed count-back, as set out in the tournament regulations. In head-to-head match play the higher single-game pinfall wins; if the format awards match points, total points decide and pinfall is the first tiebreaker.