Spin in Snooker Explained: Top, Stun, Screw and Side, and Where the Cue Ball Goes
The short version:
| Spin | Where you hit | Straight pot: the cue ball… | Cut pot: the cue ball… |
|---|---|---|---|
| Top | Above centre | follows through | bends forward of the tangent |
| Stun | Slightly below centre | stops dead | leaves at 90° (the tangent) |
| Screw | Well below centre | comes back | bends back from the tangent |
| Side | Left or right of centre | mostly changes the angle off a cushion, and the aim | |
Spin in snooker is less about making the cue ball do tricks than about making it predictable. Every shot in a break is played with one of four kinds of spin, or a mixture, and each one sends the cue ball somewhere different after it hits the object ball. This guide explains what each does and why, with the one idea that ties them together: what matters is the spin the cue ball still has at the moment of contact, not the spin you put on it.
The names: snooker and pool
| Snooker | Pool (US) | What it means |
|---|---|---|
| Top (topspin) | Follow | Forward spin; the cue ball goes on after contact |
| Stun | Stop shot (straight) / stun | No spin at contact |
| Screw (back spin) | Draw | Backspin; the cue ball comes back |
| Side | English | Sideways spin |
| Plain ball | Centre ball | No side, usually with natural roll |
Where to hit the cue ball
Two facts about a cue ball hit with a level cue explain most of spin:
- Hit at the centre, it slides first. Friction with the cloth then turns the slide into roll. By the time it is rolling naturally, it has slowed to 5/7 of its starting speed.
- Hit seven tenths of the way up, it rolls at once. On a 52.5 mm snooker ball that is 10.5 mm above centre. Above that point you add extra top; below it the ball has to slide before it rolls; below centre it has backspin.
How far does a centre-ball shot slide?
The sliding distance for a centre-ball hit is 12v² ÷ (49 μ g), where v is the cue ball's speed, μ the sliding friction between ball and cloth (around 0.2 on a typical cloth; it varies) and g gravity. That gives roughly:
| Cue ball speed | Feels like | Slides for |
|---|---|---|
| 1 m/s | A gentle positional shot | about 12 cm |
| 2 m/s | A medium pot | about 50 cm |
| 3 m/s | A firm pot | about 1.1 m |
So a firm centre-ball shot into an object ball 50 cm away arrives still sliding, and stuns. The same hit at a gentle pace has started rolling long before, and follows through. The spin you get at contact depends on where you hit, how hard you hit and how far the cue ball travels. That is why the same tip position can give stun on one shot and run-through on another.
The stun shot
A stun is a shot where the cue ball has no spin at all when it reaches the object ball. All of its motion is sliding. What happens next is pure geometry:
- Straight pot: the cue ball gives all its speed to the object ball and stops dead where the object ball was.
- Cut pot: the cue ball leaves along the tangent line, at 90° to the direction the object ball goes. Its speed on that line is the sine of the cut angle times its speed before contact, so a thin cut keeps most of the pace and a nearly straight one keeps very little.
That predictability is why stun is the most useful positional shot in snooker. If you know the cut angle, you know exactly which line the cue ball will take, and pace is the only thing left to judge.
How to play a stun
Hit slightly below centre with a firm, smooth stroke, so the backspin you create has just worn off as the balls meet. How far below centre depends on the distance and the pace: the further the cue ball has to travel and the slower you hit, the lower you need to go. On a short pot hit firmly, a centre-ball hit may already stun (see the table above).
- Cue ball comes back a little? You still had backspin at contact: hit a touch higher or a touch softer.
- Cue ball rolls through? The backspin had gone and it had started to roll: hit a touch lower or firmer.
The long blue in our snooker practice routines has a stun set: ten pots where the cue ball must stop within a ball's width of the blue spot.
Stun run-through and stun screw
Between a pure stun and full top or screw there is a range of small adjustments. A stun run-through leaves a little forward roll at contact, so the cue ball follows on a few inches on a straight pot, or bends a little forward of the tangent on a cut. A stun screw leaves a little backspin, so the cue ball comes back a short way. Together they let you move the cue ball by small, controlled amounts, which is most of what break-building needs around the black and pink.
Top
Hitting above centre gives forward spin. On a straight pot the cue ball follows through after the object ball. On a cut, the cue ball first leaves along the tangent line, then the forward spin bends it forward. With natural roll near a half-ball pot, it ends up roughly 30° from its original line, the basis of the 30° rule. Extra top, from hitting higher, bends it further and makes it run further.
Screw
Hitting well below centre gives backspin. If some of it is still there at contact, the cue ball comes back towards you on a straight pot and bends back from the tangent on a cut. The further the cue ball travels before contact, the more backspin it loses, so long screw shots need a lower hit and a firmer stroke. The snooker screw shot covers the technique.
A related shot is the drag: hit low enough to put backspin on, but at a moderate pace, so the backspin slows the cue ball down and wears off on the way. The cue ball travels a long distance quickly, then arrives at a gentle speed. Snooker players use it to play a soft shot over a long distance with less risk of the cue ball drifting off line as it slows.
Side
Hitting left or right of centre spins the cue ball sideways. Its main job is after the cue ball hits a cushion: running side (the side that matches the direction the cue ball is travelling along the cushion) widens the angle it comes off at and keeps it moving, while check side narrows the angle and takes pace off. Snooker side spin explains both with examples.
Side has a price. The cue ball leaves slightly off the line of the cue, away from the side you used (deflection), and on slower shots it then curves back (swerve), so side changes the aim. On a napped snooker cloth, side and slow-moving balls also behave differently when you play up the table and when you play back down it. That is why coaches say: use side only when plain ball, top, stun or screw cannot get you where you need to be.
How to choose the spin
- Can stun do it? It is the most predictable: the cue ball goes along the tangent, and you only judge pace.
- If the cue ball needs to go forward of the tangent, add top or a run-through.
- If it needs to come back behind the tangent, add screw.
- If the cushion angle is wrong for every one of these, consider side.
See the cue ball's path before you hit
The AimGeometry trainer draws the predicted cue ball path for top, stun and screw, including the curve as the spin takes hold. It runs in the browser, free. The practice table is a 9 ft pool table and the physics models top and screw but not side.
Try the follow and draw drills →FAQ
What is a stun shot in snooker?
A shot where the cue ball has no spin at contact. It stops dead on a straight pot and leaves along the 90° tangent line on a cut. You hit slightly below centre so the backspin has just worn off when the balls meet.
What is a stun run-through?
A stun with a little forward roll left at contact: the cue ball follows on a few inches instead of stopping.
What is the difference between stun and screw?
Both are played below centre. With stun the backspin has gone by contact; with screw some is left, so the cue ball comes back.
Where do you hit the cue ball for top?
Above centre. At about 10.5 mm above centre the ball rolls naturally from the start; higher adds extra top, up to around half the radius (13 mm) before miscues become likely.
How does side work?
It mostly changes the angle off a cushion (running side widens it, check side narrows it) and it changes the aim, through deflection and swerve.
Related reading: Snooker Screw Shot · Snooker Side Spin · The 30° Rule · Snooker Practice Routines · How to Aim in Snooker
Physics: natural roll at 7/10 of the ball's height and the 5/7 rolling speed follow from a solid sphere's moment of inertia; the sliding distance 12v² ÷ (49 μ g) assumes a centre-ball hit, a level cue and a constant sliding friction (μ ≈ 0.2 is a typical value and varies with the cloth). Figure 2 is schematic. This article contains no sponsored or affiliate links.