As long as you have good quality fabric, this is very likely the best method. If you bought your fabric at JAF/HL or if it is reproduction fabric, you probably want to fold & cut because I've found that the lower quality & loose-weave repro's end up really wonky when torn.

I have LQS by me that tears standard width fabrics. The Kona & Moda solids and new batiks turn out fine. The repro's end up as much as 1.5" off and then I lose even more when squaring up!​​

If you do fold your fabric, I recommend pressing with heavy starch (or Best Press) flat; then, fold the fabric as much as needed to work with your ruler (maybe draw three lines measuring into the fabric, then a straight line from top to bottom) and press again to make sure you don't end up with that little tab or divet where the folds are. Then cut to get your straight edge & measure/cut from there. Tearing is definitely easier if you have decent fabric.

My hands are too weak to rip fabric, but it does sound a lot quicker!

I remember learning how to square up fabric for clothing. You'd tear each side so that you'd have it with the weave. (or pull a thread and cut if tearing wasn't a good choice) Then hang it on the fold and see if the ends line up. Usually not, so you and a partner each grab the shorter corners (will be opposite -so across grain) and then PULL and check, and kept it up until you've got the grain running straight.

At least with quilts, off grain is rarely a problem, but if cut pant legs or a skirt out of off grain fabric, it's rarely going to drape correctly.

A lot of fabric gets stretched off grain in the process of dying and winding on bolts. The thing to remember, is after it's washed and relaxes, the fabric will want to go back to straight grain if gravity is pulling on it. Not fun to have your nice pair of dress pants start to have the side seam pull around to the front, and your center crease line have a nice wave to it.

Dealing with fabric for quilting is so, so much easier!

As Prism99 says,

Ripping/tearing the fabric DOES do damage to the adjacent sides of the tear. I have seen ripples/damage over two inches on each side of the tear - and some the damage is only obvious for a half inch or so on each side.

If a straight of grain cut is important to you - but you need to be miserly with your fabric, the pulled thread method is "safer" - even though a lot more tedious to do.

Just finished using a 106" backing. I glue basted it to the batting. I didn't do anything but lay it on the batting and ironed it smooth. It dried nice and flat and basted to the batting.

Honestly I don't cut it down until after all the quilting is finished. Last thing I want is a backing that ends up too small.

I make the quilt sandwich on my kitchen floor. So, I just lay the batting & quilt top on the uncut backing, positioning them at one corner with a couple inches of the backing extended on the 2 sides. I then put my big cutting mat underneath and trim down the batting & backing on the remaining 2 sides - again allowing a couple inches of extra backing. I find this to be the least waste of both backing and batting.

I want to send this out to a long-arm quilter so I need to have it sized properly.

Is it not as important to have your backing straight of grain? If that is the answer, then that will relieve a lot of my stress in figuring out how to handle such a large piece of fabric.

Most long arm quilters I know are more concerned with the backing size to be no smaller than 6 to 8 inches larger than the top. Not if it is over sized. I would not cut it smaller. I would only make sure it was cut straight. Have you checked with your long arm quilter? Or are you just assuming that since she has given you a minimum size for the back that it needs to be that exactly.

I don't often use wide backing, but I when I do any larger quilt, this is what I do with it:

* I fold the backing in 1/4's (half one way, half the other)
* fold the top in 1/4's
* set the folded top on top of the folded backing matching how they are folded
* cut the backing bigger than the top by however many inches I want it. If I want it 8" bigger overall, I cut the folded backing 4" bigger than the folded top.