Don't be scared. I know it says "math" in the title, but it's knitting math, so we can handle it, right? (Fearless knitters and all that.) Plus, we'll go slow, we'll do this in stages, you can ask questions, and there are no stupid questions, ever. OK. Now that you know the basic concepts behind waist shaping, let's talk some numbers.
Waist shaping on a simple shirt: Hem to hip
We'll do the math for a theoretical sweater for myself, using my battered-and-beloved copy of Ann Budd's Knitter's Handy Book of Sweater Patterns as a template. I'll start with the charts for a basic pullover, modified to be worked in the round.
Remember, this is a theoretical sweater, folks. No time to knit an actual sweater, but that's OK. It's just to illustrate The Numbers.
Yes, indeedie, I must theoretically knit a theoretical gauge swatch, because I need to know two numbers: stitches per inch, and rounds per inch.
Gauge: 7 stitches per inch and 13 rounds per inch.
For this part I need to know: hip circumference, hem-to-hip length, and the all-important Desired Ease. For ease, I'd like something body-skimming, but not tight. (No negative ease this time.)
Hips: 44" I measure this with my handy tape measure.
Hem-to-hip length: 2" I choose this based on the pattern and garment shape.
Ease: 1.5" (positive) ease I choose this based on how I like to wear garments of a similar style.
How many stitches to cast on?
Add together hip measurement and ease: 44" plus 1.5" equals 45.5".
Multiply by gauge: 45.5" times 7 sts per inch equals 318.5 sts.
Round up: 319 stitches to cast on at lower hem.
What to do next?
I start knitting! I work even over those 319 stitches for 2" (see hem-to-hip length, above), which works out to 26 rounds (2" times 13 rounds per inch).
Once I have finished those 26 rounds, I have reached my widest bit. It is time for the decreases to begin!
Sandi Wiseheart is the founding editor of Knitting Daily. She is now the author of the popular Knitting Daily blog: What's on Sandi's Needles.
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