How to Construct a Square With a Compass


Oftentimes, it is important when drawing up blueprints and plans to have precise shapes and measurements. A compass is a handy tool for drawing squares and many other shapes accurately. A square is a basic shape with all four sides having the same length and four 90 degree angles. The compass conveniently helps to find these angles and transfer lengths. Familiarity with some basic geometry terms will be necessary: end point, distance, perpendicular and arc.

Things You'll Need

  • Compass
  • Ruler
  • Paper
  • Pencil
  • Draw a line from the left side of your paper to the right using a ruler. Draw and label two endpoints. End point A will be on the left and end point B on the right. The distance from point A and point B will be labeled r. Distance r will be the length of each side of your square. Extend the line further to the right from point B to help in finding a new line that will be perpendicular to Line AB.

  • Draw a perpendicular line upwards from point B. Using distance r, mark and label a new end point C. This will be the second side of the square at an exact 90 degree angle.

  • Draw an arc with end point A as the center and r as the distance using a compass. Draw a second arc using end point C as the center and r as the distance. Mark and label where these two arcs meet as point D. This is the final corner for your square.

  • Connect end point A to point D with your ruler. Connect end point C to point D.

Tips & Warnings

  • Be extremely accurate when using your compass. Your square will not be perfect if your compass changes its measurement when transferring length from one side of the square to another.


  • Photo Credit Jupiterimages/ Images
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