It could be as big as you want it to be, but it is usually about a half and inch wide all the way around. The standard seam allowance is 5/8 inch.
The seam is simply the name of the line that is created when two pieces of fabric are joined together. If you are sewing any two pieces together, the place where they are joined is called the seam. Maybe you are wondering about the seam allowance, which is the amount of fabric alloted to sewing the pieces together. The seam allowance is the distance from the edge you put your line of sewing. In many fabrics that allowance can be very small, but some fabrics require a larger allowance to minimize fraying.
Before that can be answered there are couple of questions that need to be asked. Are the 10 x 10 inch squares the finished size or is that including a seam allowance? What is the width of your fabric?
Anybody answer this question......
so that the material does not fray.
The fabric between the seam and the cut edge is referred to as the seam allowance.
A seam with no seam allowance. Right sides are the same side up and you you zig zig stitch the pieces together with or without an underlay.
sew a seam with a 5/8 seam allowance. then on ONE SIDE of the allowance, trim it to half the size. don't measure just eyeball it. then press the seam allowance to one side with the [now] short allowance on top. fold the longer allowance over the shorter and press it. then flip the whole thing to the other side of the seam and press again. finally, topstitch as close to the edge as you can. flat felled seams are the strongest and are used where ever a great amount of tension exists, such as the seams on your jeans, or the shoulders in a shirt/jacket. they are also used in sports clothes.
When sewing, you'll want to leave a sewing margin (or a "seam allowance") for a couple of reasons:A 5/8" margin (the standard seam allowance) between the stitch and the edge allows for a little reinforcement, and places less stress on the stitch. This will keep the stitch from breaking easily.A margin allows you to later let out the seam, in case you need more room (for example, if a skirt gets too tight, you can loosen it if there's seam allowance).
The standard seam allowance for quilts is a "scant" 1/4 inch. There are many methods and gadgets to help you achieve this. My choice is to use a 1/4 inch piecing foot and the center needle position with a straight stitch throat plate. Check with your local quilt shop and/or your local machine distributor to see what's out there. At the quilt shop don't be nervous about asking questions with both the employees and customers as to what they use. Your machine distributor probably has a foot that will help you. If you decide to go that way, get them to show you how to use the foot and then set it up yourself, measuring the seams to be sure that you will money and effort will give you the results you expect. If you vary the width of the seam allowance the tiniest bit while piecing, you cannot line up the seams and corners of the blocks.
The seam allowance is needed to allow for extra fabric where separate pieces of fabric are joined together at seams. If seam allowances were not provided you wouldn't be able to join pieces together or your garment would end up being too small. If you look at the inside of a shirt, for example, you will see that the stitches take up fabric and that is what seam allowances are for.
Inner curves need to be clipped so that the seam allowance can spread and lie flat once the item is turned.