Quick Answer: The diamonds are the small inlaid markers spaced along a pool table’s rails — 18 total on a regulation table, six along each long rail and three along each short rail — and they give players fixed reference points for calculating bank and kick shots instead of guessing the angle. The most common approach, the three-diamond (“Corner-5”) system, assigns a number to the cue ball’s position and the target spot, then uses simple subtraction — for example, cue ball at diamond 5 minus a target of diamond 3 equals 2, so you aim through the second diamond on the near rail — to find where to aim. Below is how the numbering works, a worked example, and why the math is a starting point rather than a guarantee.
If you’ve ever heard a player say “I’m going one-and-a-half diamonds off the rail” and had no idea what that meant, this guide is the explanation. It has nothing to do with the Diamond brand of tournament tables (see the FAQ below if that’s what brought you here) — it’s about the physical markers built into every regulation table’s rails.
Pool table diamonds, by the numbers:
- 18 diamonds sit on a regulation table’s rails — six spaced evenly along each long rail and three along each short rail — a layout standard across 7-foot, 8-foot, and 9-foot tables, per the WPA’s own explainer on the diamond system.
- CB − F = T is the core formula behind the three-rail “Corner-5” system: subtract the target diamond’s number from the cue ball’s starting diamond number to find which diamond on the first rail to aim through.
- No single numbering standard exists across every instructional system — some number diamonds 0, 1, 2, 3 sequentially from a corner; others multiply every value by 10 purely to avoid fractions in the math, per Dr. Dave Pool Info’s breakdown of diamond systems.
Where the diamonds are and why they’re there
Every regulation pool table’s rails have small markers — often literal diamond shapes, though some tables use dots or other inlays — built into the wood at fixed intervals. There are 18 in total: three between each pair of adjacent pockets along the long rails (six per long rail) and two between each pair along the short rails (three per short rail), with the corner pockets themselves acting as additional zero-points in most systems. Because a cue ball rebounds off a cushion at close to the same angle it strikes it — like light off a mirror — those evenly spaced markers let a player build a numbered coordinate grid across the table and calculate a bank or kick shot’s path instead of eyeballing it.
This is a different topic from a table’s physical size or its pocket dimensions — see our pool table dimensions guide if you’re after those specs instead.
How the three-diamond (“Corner-5”) system works
The most widely taught version is the three-rail system built around the formula CB − F = T: the cue ball’s starting diamond number minus the diamond you aim through on the first rail equals the target diamond on the far side.
| Term | Meaning | Worked example |
|---|---|---|
| CB | Cue ball's starting diamond number | 5 (at the corner) |
| T | Target diamond on the far rail after the bank | 3 |
| F | Diamond to aim through on the first rail | 5 − 3 = 2 |
In that example, a cue ball starting at the corner (diamond 5) that needs to reach diamond 3 on the opposite rail after banking gets aimed through the second diamond on the near rail. Different systems (equal-distance, mirror, “Plus” systems) use the same underlying idea — a numbered grid and a simple formula — with different starting assumptions, which is part of why the numbering convention itself isn’t universal (see the FAQ above).
Byrne's Complete Book of Pool Shots
- 350 diagrammed shots including a dedicated section walking through diamond-system banking and kicking, written by a BCA Hall of Fame instructor.
- Diagram-first format — each shot gets a full-page illustration, which matters more for spatial systems like this one than prose explanation alone.
- Best starting point if you want the full system (equal-distance, mirror, Plus systems) beyond the basic Corner-5 formula above.
Setting up a practice session at home? Try Amazon Prime free for 30 days and most of the gear on this page can land on your table by the weekend.
Why the math is a starting point, not a guarantee
The diamond system assumes a cue ball rebounds at a predictable, consistent angle — but real cushions and cloth don’t behave identically table to table. Rail rubber that’s hardened with age rebounds differently than fresh K-66 cushions (see our bumper replacement guide for how cushion condition changes over 10-15 years), and cloth speed varies with nap, cleanliness, and humidity (see our pool table felt guide for how worsted vs. woolen cloth affects roll). Cue-ball spin, speed, and where exactly it contacts the cushion all shift the rebound angle too. Experienced players treat the diamond formula as a repeatable starting line they then adjust by feel for their specific table — not a number that works identically everywhere.
Aramith Jim Rempe Training Cue Ball
- Printed reference lines and a 56-page instruction manual built specifically around calling angles off the rail — a practice tool for applying the diamond-system math, not just reading about it.
- Has a beginner side and an advanced side, so the same ball scales up as your angle recognition improves.
- A different training tool than the site's own Aramith Measle training ball pick, which is built for reading spin rather than rail angles — the two solve different problems.
The bottom line
The diamonds are the 18 inlaid markers on a regulation table’s rails — six per long rail, three per short rail — and the diamond system uses them as a numbered grid to calculate bank and kick shots with a simple formula (CB − F = T) instead of guessing. Treat the math as a repeatable starting point that still needs adjusting for your table’s specific cushion and cloth condition, not an exact answer. For the physical rail hardware itself, see our bumper replacement guide; for the brand that shares the name, see our Diamond pool table breakdown.