Jedi are like snowflakes; no two Jedi dress exactly alike.
The basic Jedi costume is a simple but distinctive, non-tailored style. But one size does not fit all. Straight up and down side seams work great on svelte Obi-Wan and Qui-Gon, but can look like a sack on more curved figures. Even the simplest design sometimes needs a little fitting to accommodate the whole range of body shapes that can be found in the human population. An A-line tunic is one of those accommodations.
There is one basic reason for an A-line tunic: hips. If you have hips that are significantly wider than your waist, consider using an A-line. While there is a lot of variation in length, a typical Jedi tunic will go down past the widest part of the hips. Making a straight-line tunic wide enough to fit leaves too much fabric bunching up at the waist and hanging off the shoulders. Slitting the side seams will allow the tunic to fit better, but this variation has not been seen (at least by me) in any of the Star Wars movies, and so wouldn't be consistent with a standard Jedi style. The A-line allows the tunic to fit the body properly without looking fitted and also fit within the observed Jedi standards seen in the movies. Figure 1 shows the difference.
Your actual hip measurement isn't that important when considering an A-line. It is the difference between your hip and waist measurements that matters as shown in Figure 2. Hips are a female characteristic. The general rule is that a male figure is a triangle with the point down; a female figure is a triangle with the point up. The straight line tunic looks fine hanging off of the shoulders of the triangle pointing down. But gravity's pull is no friend to the triangle pointing up without a little extra room for the base.
If there are only a few inches between your hips and waist and your front or back profiles are not noticeably wider below the waist, then a tunic with straight up and down side seams will look fine on you; an A-line would look more like mini-skirt than a tunic. However, if your figure is something similar to a pear, go for the Aline.
One final note. Only enhanced hip measurements are adjusted for with this pattern. No extra accommodations are made for enhanced bust measurements (that other primary female feature), because I frankly don't have much to compensate for. You will need to experiment with your own fitting adjustments for that.
Before you can make a tunic, you need to buy some fabric. There are a few basic rules to follow:
The best way to be sure about how much fabric you need to get is to make the pattern pieces that you'll need and try them out by laying them out on the floor. Base your estimate on different fabric widths, and don't forget that you'll need two sleeves and front pieces.
Always pre-wash your fabric before you do anything else with it because natural fabrics will shrink. Some fabrics wrinkle terribly in a dryer. If you don't want to iron, consider a natural looking wrinkle-free blend. Or consider letting your tunic dry on a line. If you're at all unsure about what washing will do to your fabric just safety pin a small scrap of it to a towel or something, wash it and see what happens.
The pattern pieces are shown and described in Figures 3-6. Many of the measurements are based on your own body measurements like height, shoulder and arm length, etc. The best way to be sure about how much fabric you need to get is to make the pattern pieces that you'll need and lay them out on the floor. Base your estimate on different fabric widths, and don't forget that you'll need two sleeves and front pieces. The cheapest way to make pattern pieces is to tape newspaper pages together, mark them with a wide, felt pen and cut them out.
Most of the adjustable dimensions are based on heights and lengths; pay close attention to your waist measurement and make sure that the front and back pieces will fit comfortably around your body. Use a shirt that fits you to compare to your pattern pieces. The neck band can narrow or wide width, but the narrower the neck band is, the closer it will fit to you.
The curve of the hem of the front and back pieces have always been a problem for me. I never quite get them right and I need to trim the tunic to get it even when I'm ready to hem it. I always add extra fabric at the bottom so I can trim it. And if you have a larger rear end relative to the rest of you, then the back piece length will need to be longer than the front. Using the hem of an A-line skirt that fits you can help as a guide, but only if it's no longer than a knee length skirt.
Unless otherwise noted, all sewing is done with a simple straight stitch. If you have a fabric that has sides that are different (an "outer" side and an "inner" side of the fabric) then always double check to make sure that the "outer" sides are facing each other when sewing two pieces together. In the figures, the "outer" side of the fabric is gray; the "inner" is white.
Sew the back piece to the two front pieces as shown in Figure 7. The neck opening should be around 15 cm (6 in) depending on how large your neck is. Be careful not to make the neck opening too large or the tunic will not fit right.
Attach the arms to the body of the robe as shown in Figure 8. Make sure that the sleeves are centered on the shoulder seams.
Sew up the side seams from the bottom hem up the sides to the ends of the sleeves as shown in Figure 9.
Attach the neck band to the tunic as shown in Figure 10. Sewing the neck band over the shoulder seam is a little tricky. Pin the band onto the tunic and try it on. Try making the width of the seam allowance at the back of the neck narrower than on the rest of the band. This should make the neck band fit better, but this could also depend on your body type. Experiment with the fit of the neck with the pinned collar.
Now finish attaching the neck band as shown in Figure 11 by folding over the neck band and sewing it down. For best results, pin and try it on for adjustment; then press the fold down before sewing. Sew the band down by sewing close to or in the indentation of the seam you already have between the band and the tunic; stitch, "in the ditch". It doesn't have to be exactly sewn along the seam line, especially if your thread color is a close match to your fabric, but it will make the stitching on the collar less noticeable. I have sewn the collar down with two lines of stitching just to make sure it is firmly in place and the result looks fine.
Finish the sleeves as shown in Figure 12. First tuck extra sleeve fabric in at the shoulders and pin. Try it on and see how you like the fit. Make sure that there is enough fabric left at the end of the sleeves so you can hem them the way you like. I prefer a wide hem at the end of my tunic sleeves, but this is not necessary. With the shoulder tucks pinned down, tack them in place with a couple of lines of stitching. The tabards of the Jedi costume will cover these up if they're in the center of the shoulders. Hem the sleeves to desired length. Generally, Jedi tunic sleeves tend to go all the way down to the end of wrist but not over the hand.
Trim off, fold over and finish the front ends where of the tunic as shown in Figure 12 as well.
Attach the ties as shown in Figure 13. Trying on the tunic is especially important here. The ties give you an adjustable fit when wearing it, but you want to make sure that the obi and belt of the Jedi costume will cover up the ties when you put them on.
Try on the tunic and check the length. Use a mirror, have a friend help or use a dressmaker's dummy to make sure that the hem is even. The hem will be narrow because it has a curved edge, so trim it if it's too long. Hem.