To start off you will need a quadratic piece of fabric (or paper if you want to do the pattern first. You do need to fold it then). The 1/2 of the side length can only be an orientation about your final skirt length, but you may think of it in terms of about 15 cm shorter.
You will need a piece of elastic that is long enough to lay around your waist comfortably (not to tight) and long enough for you to put it on. I always find the best way is just to measure it directly on you.
Off course you’ll need some thread as well.
Next Step is to fold your fabric as shown on the diagram. Once around the middle axis and than the folded piece again around the middle.
It is very easy but sometimes one needs time to figure out the easiest of things. So thats why the
pictures.
As you may remember or not from school there is this π = 3.14 (pi). It is a constant value of the relation of circles perimeter to its diameter (they are a couple, you know).
Now you ‘ll never forget that bad joke.
So now think of your hips (HM = Hip Measuerement) as a circle with a perimeter value. Measure that value. Since this tutorial is about making a circle skirt without a zipper you should measure at your widest hips point to be sure you will be able to put the skirt on later.
Now that you calculated the radius you can use it to draw it as your center circle on the folded piece of fabric or your piece of paper. It will be easier for you, if you fix the fabric with some pins or baste it bevor you start.
Draw on the double folded corner. Start drawing the calculated radius using the corner as a center. After you are finished you can use the end points to draw the circle.
Use the same techique to draw your skirt edge. Tape measure is handy at that point couse it is longer than most ruler...
So just cut along the drawn lines. When unfold you have the pattern piece.
If you want a half circle skirt you just have to fold twice and than double your HM in order to get the inner circle twice larger (cause you folded twice instead of four times). Then proceed by calculating the radius and drawing as described. Probably cheaper to make 2 piece pattern though, rather than one.