While I'm happy to make skirts for people professionally, it's also nice to share my knowledge so that others can learn to make their own fabulous skirts. Here's an overview of the math and assembly instructions.
For waist band:
You are ultimately creating a rectangle. Measure with these units:
W = 5 inches
L = 1/2 waist circumference in inches + 1 inch
Cut on the fold.
For the skirt:
Depending on the length of the skirt, you will want different widths of fabric. For a skirt above the knee or one that sits at the knee, I recommend 45-60 inch fabric. You will need 2.5 yards. For a floor length skirt, you will need 60-90 inch fabric and 3 yards of it. A king-sized bed sheet will also work. Do not select fabric with lots of stretch (no jersey!). Instead, select sturdy fabrics with a high cotton content.
You are ultimately creating two circles (one for the end of the skirt, the other for the opening for your waist.
For the waist opening, use the circumference from your waist band measurement to determine the radius. The formula for circumference is: 2πr = c. So, divide your waist measurement by 2, and then by π.
Next, determine the desired length of your skirt. This is easiest to find if you have a skirt to measure or a friend to measure your legs. This number will be most of the radius of your skirt.
To determine the total radius of the large quarter that you will cut from fabric, add the following in inches: waist radius (A) + skirt length (B) + 2. We'll call this number "r."
Lay your fabric on the floor (hopefully you have some hardwood or tile flooring) or on a large table folded in half in the direction that gives it the largest width possible. You will measure one quarter circle on the fold and one on the opposite corner (where there is no fold in the fabric).
To map your quarter circle, you will need a pencil or chalk in a contrasting color (i.e., if your fabric is black, use a white utensil). Take a large ruler or measuring tape, and measure your "r" number from the corner of the fabric down both edges of the fabric. Mark this with your utensil. Measure this number from the corner so that the marks are 3-5 inches apart (eye-balling is OK) all the way across the fabric. Once you've made these marks, then you can cut the fabric.
After you've cut both sets of quarter circles (you should have three pieces: 1 half circle, folded and 2 quarter circles), then you can cut the hole for your waist. Take the radial number you determined for your skirt opening, and measure the circle from the corner of the fabric in incriminates similar to the large circle.
If you want pockets, cut four pieces for pockets
Now, you have cut all of your pieces!
If you want pockets, sew the openings of the pockets in place 6 inches below the waist band.
Pin and sew each quarter circle to opposite ends of the half circle alining the waist opening first. You should have a 1/2 inch seam allowance. You can pick the stitch. Do not sew the open ends together.
If you have pockets, sew the pockets together.
Take the waist band piece, fold it in half, and iron the fold. Pin the open ends to the waist opening of the skirt and sew. You're almost finished!
Trim excess fabric from the waist band if there is any. Pin and sew the open edges together.
Turn skirt inside-out and iron 10 inches of the last seam you made in half (as though parting hair or opening a book).
Pin one side of a 7-9 inch zipped invisible zipper to the seam with the zipper facing the fabric. The top of the excess zipper fabric should align with the top of the skirt's waist band. Sew the unpinned side of the zipper into the fabric with your zipper foot in place. Unpin the other side of the zipper and sew it into place. Once the zipper is sewn into place, pop the stitches that cover the zipper to reveal an expertly installed zipper. Unzip the zipper and finish sewing unsecured places.
Install a hook and eye at the top of the waistband.
Iron, pin, and sew a 1/2 inch hem to the bottom of the skirt.
You're done! Go dancing or play a concert!