by Dr. Dave, from the book: “The Illustrated Principles of Pool and Billiards” The 30° Rule

billiards.colostate.edu

If you let one finger stay, The other finger points the way.

Peace.

If you don’t know the 30º rule yet, learning it can truly transform your game. The 30º rule helps you predict the path of the cue ball after impact with an object ball. This is a very important skill to have for helping you prevent scratches, plan break-up and avoidance shots, and execute carom and billiards shots. It is also critical in being able to play precision position ... the skill that separates the great players from the good ones.

When the cue ball is rolling when it hits the object ball, and when the cut angle is between a 1/4-ball and 3/4-ball hit, the cue ball’s path will be deflected by approximately 30°.

30° deflected angle

fast

medium

slow

the cue ball’s pathis deflected by 30°

aiming line

ball-hit fraction

1/4 1/2 3/4 1

10º

20º

30º

40º

cue

ball

defle

ctio

n an

gle

half-ball hit

wide margin of error

You can use a relaxed but firm peace sign (V-sign) to visualize and apply the 30º rule:

30º

original(incoming)

cue ballpath

deflectedcue ball

path

30°

tangentline

30°

slow

fastthe faster the shot,the more you shift your hand

along the tangent line

For more information, see the April-July '04 and Feb-June '05 instructional articles and the following video demonstrations on the website:

normal video

NV B.66 − The 30-degree rule, from VEPS I NV B.75 − 30-degree rule natural-angle examples, from VEPS III

normal video