Plus System Plus System
A rule of thumb that adds the first-cushion number to the departure number on a short → long → long path. This page uses INPROD's shared departure/arrival scale.
Written and edited by TTBoys · How we write and check sources · Report an error
Sources and diagrams reviewed: 2026-10-04. Rules of thumb are practice references for a specific diamond scale and stroke. Geometric constructions are kept separate from real trajectories, and nothing was measured on a real table. On mobile, the table stays in landscape so the directions in the text match the diagrams.
Presets are comparison examples from a physics model; they do not guarantee the formula's real-world accuracy or a point.
What do you read from the layout?
- Start 20: read it on the backward extension of the aiming line.
- Target 50: the number on the third cushion, a long rail.
- First short rail 30: from 50 − 20.
Slope and correction: Don’t add a separate angle number; read the start line again. Don’t use the basic table as is in the stretch closer to the corner than 20 on the first short rail.
New to this? Start here
Plus finds the arrival number by adding the first-cushion number to the departure number. Unlike Five & Half, this path hits the short rail first. At first, follow just one line: 20+30=50.
- Decide on the white arrival 50 first, then extend the aiming line backward to read the red departure 20.
- To find the first aim point, calculate 50−20=30. Yellow 30 is one diamond from the corner on the first short rail.
- In the full diagram that follows, trace short rail ① → long rail ② → the other long rail ③. Even for the same number 30, keep the red, yellow and white positions apart.
Check yourself: On the yellow first-cushion scale, can you treat the corner as 0?
Not with the INPROD scale used here. Half a diamond from the corner is 20 and one diamond is 30. The zone near the corner is inaccurate, and you shouldn't mix it with the 15 System or Maximum Plus scales.
Departure and arrival are counted in the same direction
- Red dashed line: extend the first aim line backward to read the start number
- White line: the order in which the cue ball travels around three cushions
- Yellow line: an example of meeting the two object balls after the third cushion
A sketch of the worked example's ball layout and travel order. Where the ball actually lands depends on thickness, spin and speed.
- Read the departure number by extending the aiming line backward from the cue ball center. When you hit an object ball first, read it from the line after the collision.
- The zone closer to the corner than first cushion 20 is inaccurate. Don't simply treat the corner as 0 in the calculation.
- japong explains a different scale system and an exception for departures 0–30. Don't plug those exception numbers into this diagram's INPROD scale.
Tip position and range
- The source's basic tip position is 2 tips of side spin, high. In this diagram it is left running English; mirror the layout and it becomes right. Match the tip height and power on the 20→30→50 reference line.
- The zone where the ball turns sharply off the short rail is sensitive to power and spin. Move the first cushion a little at a time with a consistent stroke and record the actual arrival.
- Plus Two is a variant with its own scale and conditions. It doesn't mean you can always get the fourth cushion by adding 20 to this formula's answer.
In the simulator you can compare the first aim with the actual arrival. The number table comes from INPROD below; don't use the app's comparison results as real-table corrections.
Practice with the example layout
Back to the worked example and layout ↑Follow the short → long → long path of 20 + 30 = 50, then check whether the ball comes out toward the side where the two object balls sit. Hitting the first short rail does not mean the final ball layout is solved.
- Point to the cue ball, the ball you hit first and the last ball, and say the cushion order.
- Repeat the same layout 5 times and record where the first cushion and the calculated target actually land.
- If the first cushion is already off, check your aim and thickness; if the first cushion is right but later ones drift, check spin and speed. Change only one thing for the next 5.
Sources and verification
- INPROD · 3쿠션 당구 플러스 시스템 — The shared departure/arrival scale, the first-cushion scale and the high 2-tip diagram.
- japong · 플러스 시스템 — A comparison source with the same addition formula but a different scale and exceptions.
Sources may use different diamond scales and conditions. The text notes which scale it uses and the limits of what was checked; the diagrams are our own concept drawings.