Kick Shot Lab — click two balls, get the aim diamond
New here? The systems guide explains how to use the diamond system step by step. Place the cue ball and the object ball anywhere on the table. The lab mirrors the table across the rails (the mirror system), draws the true geometric rebound path, and reads the aim point back to you as a diamond number. This is the exact ideal-geometry answer every diamond system is approximating.
Reality check
This is the ideal path (angle in = angle out, sliding ball, no spin). Real cloth, spin and speed move it — use the adjustment estimator below, then calibrate on your table.
Center ball at medium speed on average cloth: the geometric line is your best first guess.
Bank Shot Lab — mirror the pocket, aim the object ball
Place the object ball, pick the pocket you're banking into and the rail. The lab reflects the pocket across the rail and draws the line from the object ball through that mirror image — where it crosses the rail is your contact point, read as a diamond number.
Honest scope
This aims the object ball at the correct rail contact point. Whether it drops also depends on the cut angle you play, throw between the balls, and your speed. The system gets you to the right neighborhood — your stroke finishes the job.
The Corner-5 System — T = D − F
The classic three-rail kick system, documented in depth by Dr. Dave (billiards.colostate.edu). Three numbers describe the shot: D where the cue ball comes from, F where you aim on the first rail, T where it lands on the third rail. Click the table to read D, set F, and the system predicts T.
Click anywhere near a rail to place the cue ball and read its origination number D.
How the three numbers are counted
D — origination
The corner pocket is 5. For each diamond down the short rail from the corner add 1; for each diamond along the long rail subtract ½. Halves and quarters are fine.
F — first rail
On the far long rail: 1 at the first diamond from the far end rail, +1 per diamond up-table. This is the number you actually aim through.
T — third rail
Counted exactly like F, on the third rail. T = D − F predicts where the cue ball heads after the second rail — then it tracks to the corner.
Assumes a rolling cue ball with running english — the spin the system was calibrated with. Stun or draw changes the rebound and breaks the prediction. Every table runs a touch long or short: calibrate with the benchmark above.
Every System, Honestly — what each one is for
There are dozens of diamond systems; four cover nearly everything in pool. Each was tuned with specific assumptions (usually a rolling ball with running english) — the table below tells you which to reach for and what it honestly can't do.
| Shot | Reach for | Why |
|---|---|---|
| 1-rail kick | Mirror system | Exact ideal geometry — reflect the object ball across the rail, aim at the mirror image. No memorization needed. |
| 1-rail bank | Mirror system (+ 2-to-1 check) | Reflect the pocket across the rail. Cross-check with the 2-to-1 track line (ball's diamonds from pocket × 2). |
| 2–3 rail kick off a long rail | Corner-5 (corner 5 system) | T = D − F. The workhorse — one formula covers a huge family of kicks. Needs running english. |
| 2-rail kick off a short rail | Plus / Plus-2 (plus 2 system) | Short-rail aim diamond maps to a shift up the long rail; 5-to-5 track line + parallel shift. |
| Kick off short rail, no english | Sid | Multiply target spot × cue-ball distance from X. Dead-ball hit; memorized numbers are approximate. |
🪞 Mirror system
When: any 1-rail kick or bank.
How: imagine the table reflected across the target rail. Draw a straight line from the ball to the reflected target — where it crosses the rail is your aim point. Read it as a diamond number.
This is what the Kick Lab and Bank Lab above compute for you. It is exact for the ideal sliding ball — spin and speed shift it from there, which is why the adjustment estimator exists.
🎯 Corner-5
When: 2-, 3- and 4-rail kicks off a long rail.
How: read D (corner = 5, +1 per short-rail diamond, −½ per long-rail diamond), pick F on the first rail, compute T = D − F for the third rail.
Calibrated for a rolling cue ball with running english. Try the solver above. Source: Dr. Dave, VEPS / billiards.colostate.edu.
➕ Plus / Plus-2
When: two-rail kicks off the short rail.
How: the short rail gets special numbering — the far corner counts as 1, then +1 every half diamond, so the three visible diamonds are 3, 5, 7. Aiming through diamond n shifts the cue ball's line n diamonds up the long rail. The Plus-2 variant (Dr. Cue) builds a 5-to-5 "track line", parallel-shifts it to the cue ball, and shoots with about one tip of sidespin.
Also assumes rolling + running english. Different cue-ball heights need slightly different tips of spin — practice the 5-5 line first.
✖️ Sid system
When: kick off a short rail to a long-rail target, hit with a dead ball (no english).
How: multiply the target's spot number by how many diamonds the cue ball sits from the reference point X. Example from the books: target 2.5, cue ball 3 diamonds from X → aim at 7.5 on the short rail.
Honest caveat, straight from instructor Bob Jewett: the memorized second-rail numbers are "off a little but easy to remember". If you dislike memorizing tables, the visual mirror method does the same job. Source: Walt Harris's Billiard Atlas via Dr. Dave.
📐 Spot on the wall & the 2-to-1 bank line
A favorite shortcut for banks: measure how many diamonds the object ball sits from the pocket (lay your cue on the table), double it, and mark that number of diamonds from the pocket along the rail — that's your track line. Parallel-shift the line until it runs just over the object ball; where it meets the rail is the contact point. It's the mirror system drawn with a cue stick instead of math — same geometry, and a great way to double-check the Bank Lab's answer at the table.
Reading the Diamonds — the 0–8 diamond chart
Every system above speaks "diamond numbers", so reading them fluently is the real skill. The numbers are positions, not just the physical inlays: a long rail is divided into 8 equal parts, a short rail into 4.
Long rail: 0 – 8
Count eighths of the rail from the corner pocket. Physical diamond inlays sit at 1, 2, 3, 5, 6, 7. The side pocket is 4, the corners are 0 and 8. "Aim at 2.5" means halfway between diamond 2 and the side-pocket side.
Short rail: 0 – 4
Count quarters from the corner. Inlays at 1, 2, 3; corners are 0 and 4. Because the rail is half as long, one short-rail diamond number covers twice the distance of a long-rail number — systems account for this in their numbering.
Diamond Drill — 10 questions, instant feedback
Reading diamonds is a trained reflex. This drill mixes three skills — reading a diamond number off the rail, picking the aim diamond for a kick, and Corner-5 arithmetic — with answers computed live by the same engine as the labs.
Press start — 10 questions, no timer, explanations after each answer.
How the math works — and where it stops
The mirror engine (Kick Lab & Bank Lab)
For a shot with n rail contacts in order r₁…rₙ, the lab reflects the target across rₙ, then rₙ₋₁, …, r₁ — unfolding the rebound path into a straight line ("mirror table"). The straight line from the ball to the final mirror image crosses r₁ at the aim point; un-mirroring one level at a time gives each subsequent contact. A path only counts if every crossing lands on a real rail segment, in order. For multi-rail kicks the lab tries every legal rail sequence and keeps the shortest clean path (or the one through your chosen first rail).
Angles are read from that geometry: with an ideal sliding ball, angle-in equals angle-out at every rail — the lab shows both so you can see the symmetry. Diamond numbers are rail fractions: long rail = x/W × 8, short rail = y/H × 4.
Adjustment rules of thumb (estimates)
| Factor | Effect on the rebound | Rule of thumb |
|---|---|---|
| Running english | Widens the rebound angle | Aim ≈ ¼–½ diamond farther along travel |
| Reverse english | Shortens the rebound angle | Aim ≈ ¼–½ diamond shorter |
| Firm speed | Cushion compresses, angle shortens | Aim ≈ ¼ diamond shorter |
| Soft speed | Rail grabs the ball, angle widens | Aim ≈ ¼ diamond longer |
| Worn / slow cloth | Paths "track short" | Aim ≈ ¼ diamond longer; re-benchmark |
These are player-tested starting points collected from instructional literature — your table, tip and stroke will differ. The lab draws them as an aim zone, never a false-precision single point.
Sources
Corner-5 & Plus systems: Dr. Dave Alciatore's Billiards Digest articles — Corner-5 (Nov 2010), Plus System (Aug 2010). Sid system: Dr. Dave's Sid System page (Walt Harris's Billiard Atlas via Bob Jewett). Diamond-system kicking intro: Kicking Academy (Dead Aim). General FAQ: rec.sport.billiard FAQ. Explanations on this page are written fresh; formulas are standard published arithmetic.
What no diamond calculator can promise
Diamond systems are aiming guides, not physics engines. The geometry is exact for an idealized ball — but throw between ball and object ball, accidental spin, speed, cushion compression, cloth wear, humidity and even table level all move the real path, typically by a quarter to a half diamond. Anyone selling you a formula with five decimal places (like the infamous D = T/(V·sin A) floating around calculator farms) is selling fiction. Use systems to reach the right neighborhood in seconds, then let practice and table calibration do the rest.
Diamond System FAQ
What is the diamond system in pool?
The diamond system is a set of aiming methods that use the diamond inlays on pool table rails as numbered reference points. Instead of guessing rebound angles, you read a number where the cue ball sits, do simple arithmetic, and get the diamond to aim at on the first rail. The best-known versions are the Corner-5 system for multi-rail kicks, the Plus/Plus-2 system for two-rail kicks, and the mirror system for one-rail kicks and banks.
What are the diamonds on a pool table for?
The diamonds (also called sights) are visual reference markers that divide each rail into measurable segments. Players use them to aim kick shots and bank shots: each diamond is a numbered aiming target, so a rebound path can be described as "aim through diamond 3" instead of guessed by feel. They are the foundation of every diamond aiming system.
How many diamonds are on a pool table?
A standard pool table has 6 diamond inlays on each long rail (3 between each corner pocket and the side pocket) and 3 on each short rail, 18 total. For aiming math the rails are numbered as positions: the long rail is divided into 8 numbered segments (0 at the corner, 8 at the opposite corner, side pocket at 4) and the short rail into 4 segments (0 to 4).
How does diamond numbering work (0-8)?
On a long rail, number the positions 0 to 8 starting at one corner pocket: each number is one-eighth of the rail length. Physical diamond inlays sit at 1, 2, 3, 5, 6 and 7; the side pocket is at 4; the corners are 0 and 8. On a short rail, number 0 to 4 with inlays at 1, 2 and 3. Fractional positions like 2.5 mean halfway between diamond 2 and diamond 3.
How do you use the diamond system for kick shots?
Pick the system that matches the shot. For one rail, use the mirror system: imagine the object ball reflected across the rail and aim straight at that mirror image — where the line crosses the rail is your aim diamond. For two or three rails off a long rail, use Corner-5 (T = D − F): read your origination number D, choose a first-rail number F, and the formula gives the third-rail target T. For two rails off a short rail, the Plus system maps a short-rail aim diamond to a shift up the long rail.
What is the Corner-5 system in pool?
Corner-5 is the classic three-rail kick system, documented in detail by Dr. Dave (billiards.colostate.edu). You assign three numbers: D, the origination number (the corner pocket is 5; it rises 1 per diamond down the short rail and falls 1/2 per diamond along the long rail); F, the first-rail number (1 at the first diamond from the far end rail, increasing up-table); and T, the third-rail target. The formula is T = D − F. It assumes a rolling cue ball with running english, and every table needs a small calibration.
What is the Plus-2 system for two-rail kicks?
The Plus-2 (basic two-rail kick) system, popularized by instructor Tom Rossman (Dr. Cue), aims two-rail kicks off the short rail. The short rail uses modified numbering where the far corner counts as 1 and each half-diamond adds 1 (the three visible diamonds become 3, 5 and 7). The system gives a "track line" — for example a 5-to-5 line — that you parallel-shift to the cue ball, shot with about one tip of sidespin. Like all diamond systems it is a starting line you fine-tune on your table.
What is the mirror system for bank shots?
The mirror system (also called the mirror-table method) is pure geometry: reflect the target across the rail in your mind, draw a straight line from the ball to that mirror image, and aim where the line crosses the rail. For a bank shot, reflect the pocket across the rail and aim the object ball at the crossing point. It gives the ideal angle-in-equals-angle-out line; spin, speed and cloth then shift the real result slightly.
How do you measure a bank shot angle in pool?
Ideally the angle into the rail equals the angle out. To find the aim point, use the mirror method: imagine the pocket reflected across the cushion, draw a line from the object ball through that reflection, and where it meets the rail is the contact point to aim at. Read that point as a diamond number (e.g. diamond 2.5 on the long rail). Then adjust for reality: running english widens the rebound, reverse english shortens it, and firm speed tends to shorten the angle.
What angle does a kick shot come off the rail at?
With no spin and medium speed, a ball rebounds at roughly the mirror angle: angle in equals angle out. Rolling follow and running (outside) english widen the rebound angle; draw and reverse (inside) english shorten it. Faster, firmer hits compress the cushion and tend to shorten the angle slightly, while very soft hits let the rail grab the ball and widen it. Diamond systems bake in one assumed combination — usually a rolling ball with running english — which is why calibration on your own table matters.
Does spin change where a bank or kick goes?
Yes. Sidespin (english) is the biggest factor: running english — spin in the direction of travel along the rail — widens the rebound angle, while reverse english shortens it. Topspin/follow also widens the rebound off the first rail; backspin shortens it. Speed matters too: firm shots shorten the angle, soft shots widen it. Expect roughly a quarter to a half diamond of shift per factor, and treat any calculator output as the center of that adjustment range.
Do diamond systems work on 7ft and 8ft tables?
Yes. Diamond systems use diamond numbers, which are relative positions on the rail, so the same numbers apply on 7ft, 8ft and 9ft tables — the diamonds divide every table into the same fractions. What changes is the absolute spacing: diamonds are closer together on a bar box, so read fractional diamonds (halves and quarters) more carefully. Bar tables also tend to have livelier rails, so re-run the calibration benchmark when you switch tables.
Can you use the diamond system for snooker or 3-cushion billiards?
The geometry is universal, but the classic systems were tuned for pool tables. Snooker tables have no diamond inlays at all, so players use the mirror method visually instead. Carom (3-cushion) billiard tables do have diamonds and entire books of systems exist for them — the Corner-5 system actually originated in carom billiards — but the numbering and adjustments differ from pool, so use carom-specific references for that game.
Why do my bank shots keep missing even when the angle looks right?
The usual culprits: (1) throw — the object ball skids slightly off the expected line on contact; (2) spin you didn't intend — even a little accidental english changes the rebound; (3) speed — firm banks play shorter than soft ones; (4) aiming at the diamond instead of the contact point on the cushion nose; (5) table variance — rails and cloth differ table to table. Fix it by calibrating: shoot the same bank at three speeds with center ball and note where each actually goes.
How accurate are pool diamond aiming systems?
Treat them as precise guides, not physics simulations. The geometry (mirror method) is exact for an ideal sliding ball, and systems like Corner-5 were validated against real tables by instructors. But throw, spin, speed, cushion compression, cloth wear and humidity all move the real path — typically by a quarter to a half diamond. Use the system to get the right neighborhood fast, then fine-tune by feel on your table.
What is the Sid system in pool kicking?
The Sid system (from Walt Harris's Billiard Atlas, via instructor Bob Jewett) aims kick shots off a short rail to a long-rail target. You multiply the target's spot number by how many diamonds the cue ball sits from a reference point X: for example target 2.5 with the cue ball 3 diamonds from X gives an aim of 7.5 on the short rail. It is a handy no-english system, though its memorized second-rail numbers are approximations — the mirror method is the easier visual alternative.