Buying your fabric
Stretchy fabric comes in two types: stuff that stretches in all directions, and stuff that only stretches across. You don't want the stuff that only stretches across, so what you need to ask for is 'four-way stretch', not two-way.
Ask for samples if you're buying over the internet because there's nothing like feeling the fabric for real to find out whether you actually like it - pictures are only good for a general idea. Many mail-order shops will be happy to send a few free samples, but will almost certainly charge if you want a sample of almost everything.
The only real way to know exactly what length of fabric to buy is to make the pattern pieces and see how best to arrange them into the width, but to make the pattern pieces you need to know how much to scale them and you can't know that until you know how stretchy your fabric is. So either make your pattern up with... oh, 90% scaling and work out how long you need, or just buy a bit more than your height until you know how your girth affects things. I'm 5'10, 177cm tall and tend to buy 2mx60" (6'6x60") for a footed catsuit because it's easy to remember and many shops only sell whole meters. When I was starting out, I usually bought twice as long on the grounds that I'd make a mistake, and that if I didn't make a mistake I got an extra suit or something.
You may need extra: if you're using patterned cloth, you may want more in order to ensure that the design lines up in some particular way; if you're making a zentai, you'll want something like three head-heights extra.
Fabric typically comes in two widths: 60" (152cm) and 45" (114cm). Curiously, I don't recall ever having seen 4-way stretch in 45", although I have seen 2-way stretch in 60" wide. Obviously, if your widest pattern-piece is more than 45" you can't use 45" fabric without extra seams.
Oh, a final note: I'd discourage you from trying to squeeze more pattern pieces into a shorter length by twisting them around: Fabric usually stretches differently along and across, and unless you keep all pieces aligned, you may end up with odd effects. Turning pieces upside-down is usually fine unless you have a pattern or fur to deal with. If you do twist things, the suit should still be wearable even if it looks odd.
Measure your fabric's stretch
- Take your fabric and fold it roughly in half with its long edges together. The short (cut) edges won't be quite aligned because shops find it hard to cut at exactly 90 degrees, but we'll attend to that later.
- Measure about a foot along the fold from one end and hold 100mm of the fold against your rule. (See picture.) Stretch the fabric out firmly, but not so firmly that it doesn't return to 100mm when you let it go, and see how far it stretches. This is the 'vertical stretch'. (In the picture I'm holding it at 100mm and 200mm, and it stretches out 70mm, so that's 70% stretch which is about typical for normal athletic lycra.)
- Grasp a fold of the fabric in about the same area, perpendicular to the fold, and do the same thing. This is the 'horizontal stretch'.
- Make a note of these measurements. Your fabric should have at least 30% stretch in both directions (at the same time), or it could be hard to move in the finished garment.
To make the suit fit nicely you will need to scale the body measurements you take. To start with I suggest you just reduce them to 90% - that's simply multiplying them all by 0.9 and writing the results down alongside the original numbers. This will be mentioned later.
Once you've made a suit, you'll get to know where you want it to be tighter or looser, and you can change how you scale: you may wish to scale circumferential measurements differently to longitudinal ones since fabric tends to stretch more across than along; you may also wish to scale the legs differently from the body if the crotch is too loose or tight.
I have written a page that is a purpose-built calculator which I use for
scaling measurements and calculating distances, and it will even warn you if
you try to use too tight a scaling, but might be a bit boggling.