From Kristin: This fantastic tutorial and the next were written by Bethany. You can read her introduction here, and see more of her New Vintage Wardrobe creations on her blog, Bitter Betty Blogs.
Supplies
You will need:
Wrapping paper.
5th grade math skills or a calculator.
Pen or pencil
Measuring tape.
Straight edge.
The courage to face your measurements.
To draft this pattern which you will need you waist measurement and the total length that you would like the skirt to be. Also take your hip measurement to check against the pattern to make sure the skirt will give you adequate coverage! Measure where your waist where you want the skirt to sit. I measured at my true waist for this one because I am going for That “Audrey Hepburn” retro chic deal. (Funny because my geometry is all based on a disco wrap pattern I found at the thrift store. Ha.)Was that painful? Remember they are just numbers and this is a wrap skirt so when they go down you can just cinch it in. Now, how long do you want it to be? Measure from your “waist” to where you want the skirt to end. Mine is 33 inches, but I am doing a pattern for a friend that is 20 inches. Her’s is more “knee length with high hip wrap”.

Okay.. Now the math. It’s easy!
“Waist” plus 6 inches for the overlap, plus 2 inches for the seam allowances.
Now divide by 4.
Viola: waist number!
Hip # Just to check your coverage…same math.
Length: total length –1 inch (waist band offsets the seam allowances with 1 inch difference.)
Bottom width: For a Long skirt (33 inches) you multiply “waist math answer” by 2.75
For a knee length (20 inches) you multiply “waist math answer” by 2.25

I won’t go into how risky (or should I say risqué??) the whole ‘Mini wrap skirt thing’ might be, but I haven’t tested the geometry. Likely, the ‘knee length math’ should work pretty well.

Now when you draft you pattern I find old wrapping paper is pretty useful.

Start at the top right of your paper..

Drop down a few inches and then make a horizontal line the length of the waist math answer:
(W + 6+2 divided by 4)Make another line from the front tip of the waist measurement down the paper using the Length # ( L -1)
Now at the bottom of that line make another horizontal line this time using the bottom width equation.
Draw a vertical line straight up, about 18 inchesNow go above the first mark you made and on the top of the far end measure up 3 inches for a “true waist” and 2 for a “high hip.”
I used a pattern for a guide but can use a “belt curve” that they have at sewing stores or a steady hand and keen eye. Make it a smooth as possible though, as your bottom curve is based on this line.Now From the top of that curve use your straight edge to connect that point to where it intersects with the vertical line you just drew.
Check about 7 inches down… make sure your skirt is wider than your Hip math result
( H+6+2 DIVIDED BY 4)Move the top of your straight edge down the curve measure your length and make a dot… repeat … and press repeat … repeat.
Connect the dots. Neaten the curve.
Write on your pattern “Place On fold “ down the front of the first line you drew.Some where on there write, “cut two”.

Cut it out. The pattern, I mean.

Go shop for fabric. Two fabrics that look good together.EDITED:  If you are going to use 44″ wide cotton, you need about 3–3.5 yards of fabric for each side.  See this post:  http://www.sewmamasew.com/?p=104.For sanity’s sake I picked two that I was certain would wash/ wear and weigh similarly. It just makes life easier.I picked two nice quilting weight cottons.
Coming up… Wrap Skirt Construction!