The circle is, in my apprehensive opinion, the Queen of the geometric shapes. Don't get me wrong; I like all those squares, rectangles, triangles, octagons, and whatnot; but the circle is the coolest of the bunch: smooth and pretty and incessantly useful. Still, trying to draw a perfect circle without a pattern is a challenge, and figuring out the proper size of an opening into which a circumvolve tin can be inserted requires working with Pi (or π), which is non the delicious kind you lot can swallow with a chip of ice cream. Nosotros're here today to help y'all with the steps y'all've forgotten since loftier school geometry class (or maybe never learned because you were as well busy passing notes with Susan Ellery!). Nosotros'll evidence you the parts of a circle, how wide to cut cloth to fit a circle, and how to draw a circle without a pattern. We've also included a handy conversion from decimals to inches, which is necessary when working with Pi.

The parts of a circle

Allow's start with remembering what all the parts of a circle are called and how Pi (π) fits into the mix.

Radius: the distance from the center of the circle to the exterior edge

Diameter: the distance across a circumvolve through its center point

Circumference: the distance effectually the outer edge of a circle

π or Pi: the name given to the ratio of a circle'south circumference to its bore, expressed equally the decimal 3.14

How broad to cut textile to fit a circle

If yous know the diameter of your circle, you can apply a standard formula to figure out the width of the fabric cut needed to brand a tube. That width is the circumference of the circle that will exist inserted into the tube (we have a swell step-past-step tutorial on how to insert a circle into a tube).

The formula: three.14 (π) 10 diameter = circumference

Example: You want a finished 12″ diameter base (a 12″ bore circle) in a duffle bag.

3.14 x 12 inches = 37.68 inches

(This works with the metric system likewise: three.xiv x 30 cm = 94.2 cm)

An of import step many people miss at this indicate is forgetting to add extra (to both pieces) for the seam assart. If you lot employ a standard ½" seam allowance, you need to add together ane″ to the diameter of your circumvolve ( the diameter increases by double the seam allowance)and one″ to the width of your material (½" for both sides of the seam allowance). In our instance, that means:

The circle should start as 13″ in diameter.

The material should exist 38.68″ in width

The height of your cloth cut is variable and dependent on your project. For example, a alpine duffle bag might be thirty″ in peak whereas a shorter bucket might be just 10″.

Converting a Decimal to a The states Ruler Measurement

If you lot are using Pi, remember it always returns a decimal number. If you already bargain with the metric system, you rock –  no conversion necessary.

For those of us in the earth of inches, you need to find a yardage conversion.

In our case nosotros have 38.68 inches. Harumph! The tabular array beneath will requite yous a close-enough ruler match.

The decimal .68 is closest to .63 or ⅝". We tin can use 38⅝" as the width of the cloth piece you are cut for your tube.

How to Draw a Circle

If y'all have a supply of large compasses, you're in luck, and tin can easily draw yourself all sizes of circles. But you can also easily make your ain compass to depict a circle.

To beginning, you need to know how big you lot desire your circle (the bore). For our ongoing example, we desire a xiii″ diameter circle

To draw a circle yous need to know its radius. As you learned above in the kickoff section, the radius is one half of the bore. In our example, ane one-half of 13″ is 6½".

The full circle method

  1. Use a sail of lightweight paper (graph or pattern newspaper works well) that is at least i″ larger all around than the circle you want to describe.
  2. Cut a piece of string about 4″ – v″ longer than your radius. We used a x″ length of string.
  3. Tie one end of the string to a short pencil.
  4. Place the point of the pencil toward the outer edge of the paper with enough room from the edge to make a full sweep.
  5. Measure from where the bespeak of the pencil touches the paper backwards by the length of the radius (in this example 6½").
  6. Pin directly through the string into the paper at that exact point.
  7. Keeping the string taut, describe a perfect circle using your homemade compass.

The folded quarters method

  1. Once again, start with a foursquare of lightweight paper at to the lowest degree i″ larger than the circle y'all desire to draw.
  2. Fold the paper into quarters. Make sure your original foursquare is even and true! Position the paper with its folded edges along the lesser and left side and the open edges forth the top and right side.
  3. Place a see-through ruler at the exact center of the lesser left corner of your folded square. Swing the ruler from the tiptop to the bottom of the square, like a pendulum or compass, measuring and marking a dot at the 6½" point in three to iv spots. You are creating a semi-circumvolve arc. Make sure the end of the ruler at the corner bespeak doesn't shift position.
  4. Cut along the arc through all the layers and unfold the finished 13″ circle. You can now use this paper pattern to cut your textile circle.

With your spiffy new circumvolve, you can at present sew together the side seam in the main fabric cutting. Then pin the base of operations to the resulting tube and sew the tube to the circumvolve using a ½" seam assart. The result is a 12″ diameter finished base of operations.

Equally mentioned above, for more on this technique, run into our tutorial: How to Insert a Flat Circle Into a Tube.