The G2 I & J Calculation Method is a crucial aspect of CNC programming for creating precise circular arcs. G2 is the Gcode for clockwise circular interpolation, which, along with I and J, defines the size and location of the arc to be cut.
Usage Format
The standard format for a G2 command in CNC programming is:
G2 X_ Y_ I_ J_
Where:
 X and Y are the end points of the arc.
 I and J are the distances from the starting point to the center of the arc along the X and Y axes, respectively.
Explanation
The I and J values are incremental distances that determine the arc’s radius and its center relative to the starting point of the arc. By calculating these values correctly, the machine can accurately follow the desired path.
Example
Consider we need to program a clockwise arc that starts at point (2,2) and ends at point (4,2), with a center at (3,3).
Here’s a text diagram to illustrate:
(3,3) Center of the arc


(2,2) Start  Arc > (4,2) End
The Gcode for this operation would be:
G2 X4 Y2 I1 J1
Explanation:
 We start at (2,2), and our end point is (4,2).
 The center of the arc (3,3) is 1 unit above and 1 unit to the right of our starting point, hence I1 and J1.
By following this method, CNC programmers can ensure that their machines produce accurate and consistent arcs, which is essential for highquality machining operations.