I don’t expect you to understand this, especially considering that I didn’t even include all of the measurements.
This, ladies and gentlemen, is an example of the sorts of calculations that go into making a pattern mathematically, and a rough duplication of the base pattern that I used for my summer dress (the final result has some differences that I added in after a couple of fittings). I had wanted to post pictures of the original pattern, but the cats — being cats — had discovered it and destroyed it before I remembered to properly put it away.
Make sure that you’re properly familiar with how to take measurements.
Anyway, the very first line to start with is the back-waist length measurement. That will go from the highest point in the shoulder down to you waist. Next comes your armhole depth, which I like to measure by putting on a comfortable shirt and measuring around my shoulder from the top seam to the armpit seam. For some weird reason, all of the measurement tutorials that I’ve seen on-line never mention this one, despite how important it is. Whatever number you get, go down that far from the top of the back-waist line, add ease, and mark it.
Next is the bust. Divide your bust by 4, then draw a line perpendicular to the back-waist line at the armhole depth point, making it as long as a quarter of your bust measurement. At this point, you can draw a line of the same length at the top and bottom of the back-waist line, and close the rectangle on the other side.
The dart is made by multiplying your quarter bust number by 2/3, and measuring that far from the side of the pattern that will be your front. Draw a perpendicular line at that point, then measure 2″ down from the bust line and mark it. The size of the dart is determined by subtracting a quarter of your waist measurement from a quarter of your bust measurement, and distributing it evenly on either side of your perpendicular line where it meets the waist. Draw straight lines from the points up to the mark that is 2″ below the bust line.
The size of the armhole is determined by taking a quarter of your bust measurement and subtracting half of your back-width measurement. Measure that amount in, then square it up to the topmost line, making sure that you’re working with the back side of your pattern. You can get the curve of the armscye by measuring two inches down from the top of the back-waist line, and drawing an angled line to the point where you want your neckline to begin. Measure halfway along that angled line, then connect that point to the middle of the armhole line (yes, I’m getting flippant. This is incredibly boring to write) using a gentle curve. Smooth out the underside of the armscye as well.
Draw your neckline.
And that’s how you make the front half of a very basic pattern. I’ll probably never do instructions like that again.