AutoCAD Tips & Tutorials

Find the midpoint between two points or the center of a triangle

Use AutoCAD's calculator (the CAL command) to find calculated points, such as the midpoint between two existing points or the center of a triangle. You usually use this command transparently, while drawing a line.

For example, to start a line midway between two points, do the following:

1. Turn off OSNAP, so you don't inadvertently snap to an object snap, especially if you're near other objects. 

2. Start the LINE command. 

3. At the Specify first point: prompt, type ‘cal and press Enter.

4. >> Expression: Type (end+end)/2 and press Enter.

5. >> Select entity for END snap: Use the pickbox to pick a point.

6. >> Select entity for END snap: Pick a second point.

7. Continue drawing the line.

The line starts at the midpoint between the two points you specified. 

To use circle centers, type (cen+cen)/2.

There's an object snap for just this purpose. With OSNAP on, start the LINE command. Shift+right-click and choose Mid Between 2 Points from the shortcut menu. At the First point of mid: prompt, specify the first point. At the Second point of mid: prompt, specify the second point. Then, continue to draw your line.

To start a line at the center of a triangle, you use a similar technique:

1. Turn off OSNAP, so you don't inadvertently snap to an object snap, especially if you're near other objects. 

2. Start the LINE command. 

3. At the Specify first point: prompt, type ‘cal and press Enter.

4. >> Expression: Type (end+end+end)/3 and press Enter.

5. >> Select entity for END snap: Use the pickbox to pick a point.

6. >> Select entity for END snap: Pick a second point.

7. >> Select entity for END snap: Pick a third point.

8. Continue drawing the line.

The line starts at the center of the triangle, as you see here.

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