As far as calculating the radius for your waist, I liked Fickle Sense's post because it gives you the calculations for full, 3/4, 1/2 and 1/4 circle skirts.
So that was very good information to have. But I still wasn't sure how to be able to create a maxi length circle skirt. Enter Niler Taylor. I LOVE HER! She has tons of great videos on her YouTube channel. But mostly I love her because she gave me the final piece of information I needed to create the maxi length circle skirt. This video does a very good job of showing you how to calculate how much fabric you need to purchase and how to combine the fabric to make it wide enough.
I found this several months ago but hadn't yet taken the plunge. In my haste (it was Wednesday and I needed to finish a dress for a party on Friday), I completely forgot Niler's instructions to use double the finished skirt length of fabric. I had just combined the pieces together when I realized my mistake. I didn't have anymore fabric so I wouldn't have had enough to do it Niler's way that night anyways.
Then I remembered a video that Mimi Goodwin recently posted. In Mimi's video, the way she folded the fabric is what ultimately saved me from scrapping 3 yards of fabric. So basically what I did was cut out a 1/2 circle. The next day (it was late and the stores were closed already) I purchased 3 more yards of fabric, cut out another 1/2 circle and combined the two together. In hindsight, this may have proved to be the better method for the amount and type of fabric because I ended up with my back seam already open - rather than having to cut it myself.
So now the skirt is ready to be hemmed. Gertie's New Blog for Better Sewing has a two-part video on hemming circle skirts. Two things were important here. Most importantly that you should let the skirt hang before hemming it because part of the skirt will be on the bias and it will stretch quite a bit. And it did stretch. I believe Gertie recommended letting it hang for two days. Well I didn't have two days. I had overnight. I wanted my dress to just kiss the floor with my heels on. I had put on the shoes I intended to wear before measuring the length of the skirt. So when it was time to hem I put on my shoes and in front of the mirror for HOURS and pinned and repinned. Gertie has an excellent method of marking the hemline. Be sure to watch both videos.
Well that just about covers the sources I used to create the skirt for this dress.
But before I leave you, a couple of days after I finished this dress, I saw this post on By Hand London's blog. They released an app which does the calculations for 1/4, 1/2 and full circle skirts. You enter your waist measurement and the length of the skirt and it gives you the radius and tells you how much fabric you need to purchase. You have the option to enter either inches or centimeters. Now it does have the limitation of the width of the fabric but we've already covered the work-around for that.
I hope this post has been helpful. Happy sewing!