In an isometric drawing, what angle are the horizontal planes drawn above the horizon?

• A. 45 Degrees
• B. 30 Degrees
• C. 60 Degrees
• D. 15 Degrees

Answer: (B)

In isometric drawing, horizontal lines are drawn at 30 degrees above the horizon. This angle comes from projecting the three principal axes so they’re equally foreshortened, which makes the X and Y directions appear as lines leaning up from the horizon by 30 degrees on opposite sides, while vertical lines stay vertical. That 30-degree tilt keeps the horizontal planes’s edges consistent with the isometric scale. Other angles would disrupt that equal foreshortening, which is why 30 degrees is the correct choice.