Circle Skirt Math

QUIT FREAKING OUT.

I have your back on the math portion of this. I promise. It's not hard! If you were awake during middle school math, you'll be okay.

Let's look at what our eventual goal is. We want a piece of cloth that looks like this:

The name of the game is understanding that we've got two concentric circles going on here. One circle is the smaller inner circle that we've cut out. The other circle is the outer circle that eventually becomes the hem. We have to draw both of them on the cloth before we cut.

See the line in the diagram, the cut? That line is however long you want the skirt to be, plus a half inch for a hem. If you want a four inch long skirt, that line is 4.5 inches. If you want a six inch skirt, 6.5. Make sense? You get to make that number up.

We know the circumference of the inner circle. It's whatever your doll's waist measurement is, plus a good 1.5 inches to get velcro on the back edge of the skirt. (You are welcome to add less or more to this number, but add SOMETHING, otherwise the skirt won't go on your doll.)

Finally, just for fun and profit, we know where the center of the circle is just because we're the ones who get to make that up.

Therefore:

The diagram is a color-coded version of what we know and need to know. You can see a key on the note card. We need to know the inner circle radius and the whole circle radius so we know how to set our compass to draw on the cloth. (We could, if we wanted to, calculate the outer circle's circumference, but we don't really need to.)

So yeah, those equasions look all nice and such, but how do you use them?

Observe. Here it is, in my own handwriting:

That's all! I'll even let you use a calculator. Now get back to making a circle skirt.

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