The Project: You want to make a round, bucket-type tote bag. You want the bottom worked in a solid stitch - like a single crochet. You want the top worked in a lacy stitch pattern, like shells.
The Problem: How do you figure out how many rounds of the solid stitch to work for the bottom? How do you figure out how many shells to work, and how to space them?
The Answer: Decide how wide you want the tote, when it's folded flat. That will be the approximate diameter of the bottom circle. (For those of you who were dreaming of your boyfriend or girlfriend during your high school geometry class, the diameter of a circle is the line drawn from edge to edge through the center of the circle.) So, crochet a circle that will be approximately that diameter. You can end each round, or crochet in a spiral. This is up to you. But if you're crocheting in a spiral, and not ending each round, you still should end the last round. Do this: when you get to the last stitch of the round (you did mark the last stitch of each round, didn't you?), do your stitch in the last stitch, and then slip stitch in the next stitch. Of course, I'm assuming you're working in single crochet. If you worked your circle in double crochet, you should end your last round with 2 half double crochets, and then 2 single crochets. That should get you to the last stitch. Then do a slip stitch in the next stitch. If you worked your circle in half double crochets, then end your round with 2 single crochets. Then slip stitch in next stitch.
Okay, are you with me so far?
Next step - decide the stitch and stitch pattern you want to use for the sides of the bag. Once you have that, figure out the repeat count. How many base stitches does each repeat take? Divide that number into the number of stitches in your last round of the bottom circle. Hope it divides evenly. If it does, then you can space the stitches so that one pattern repeat will take up the same number of stitches as the answer to the above division problem.
Here's an example.
I have 90 stitches in my last round. I want to work a shell pattern that uses 4 base stitches per repeat. Here is the pattern:
*sc in first stitch, skip one stitch, (2dc, ch 1, 2dc) in next stitch, skip one stitch. Repeat from * around.
Do you see where the pattern takes up 4 stitches per repeat?
"sc in first stitch" - that's one.
"skip one stitch" - that's two.
"(2dc, ch 1, 2 dc) in next stitch" - that's three.
"skip one stitch" - that's four.
Okay, you have 4 stitches per pattern. And 90 stitches all together. 90 divided by 4 = 22.5. Oh oh - it's not even. So my pattern repeat will not be able to repeat the full pattern at the end. So I have to do something.
I need to change the pattern repeat to some number that goes into 90 evenly. Like 6. If I skip 2 sts between the sc and the (2dc, ch 1, 2 dc) shell, on both sides of the shell, that will add 2 more stitches to each pattern repeat, giving me 6 stitches for each pattern repeat. And 90 divided by 6 = 15.
I might have to do one more thing to the shell, so it doesn't get too stretched out trying to spread over so many stitches. I may have to add a ch-1 on both sides of the dcs.
Here's my new pattern:
*sc in first stitch, skip 2 stitches, (ch 1, 2 dc, ch 1, 2 dc, ch 1) in next st, skip 2 stitches. Repeat from * around.
There - that should do it. My stitch pattern takes up 6 stitches.
Here is the breakdown.
"sc in first st" - that's one.
"skip 2 stitches" - that's two and three.
"(ch 1, 2dc, ch 1, 2dc, ch 1) in next stitch" - that four.
"skip 2 stitches" - that's five and six.
Here's a picture of the bottom of the bag - a circle - with the first row of the side shells. You can see that there are 15 shells around the perimeter.
And here's a close up picture of some of the pattern repeats. You can see that each repeat uses up 6 sc stitches along the last round of the bottom.