I totally get that. So here we go. This only took me an hour and a half... I suck at math.
First of all, figure out exactly how big you want the quilt to be. Normally I use warm & natural queen sized, which is 90 x 108. I knock 8 inches off of that, so that I have a lot of flexibility when I'm actually doing the quilting, later on. So that leaves you with 82 x 100 as the actual queen size.
Then, figure out how big you want the coins to be - especially the width, you don't need to worry so much about the height at this moment. When I did it, I did 5" across, with 5" sashing, just to keep everything even. You want to keep in mind how wide you want the border to be - even if it's just that you know that you want it to be closer to 12" rather than 4." So you need to figure out how many columns of coins and sashing you want - say you want 7 columns of coins and 6 columns of sashing. Then we take 13 (the total number) x 5 (the finished width of the coin) and we know that the main pieced part of the quilt is going to be 65" across. We also know that your sashing needs to be 5.5" wide by the length of the main pieced part + .5" including seam allowances, and that your coins fabric needs to be at least 5.5" wide. We also know that your border at that point is going to be 82-65= 17" total, or 9.5" on either side. This number's kind of important as well, as I'm assuming you want the borders even all the way around. Using this, we can figure out how high the coins will be (approximately.) we take the 100, and subtract 17", and we have 83" as the height for the main part. There is no sashing to figure in this, so all we need to do is make 83 divide somewhat evenly (there's a bit of flexibility here, so don't worry about crazy shit like 1/8ths or 1/32nds of inches. This is why we leave more batting.) I think that 2.5" is a good height for the coins, so we'll just use that.
Now we know that the coins are going to be cut to 3 x 5.5, and you're going to need 33 or so of each of them in each of the columns (x 7 columns). so 231 coins (by this point my math may be out, I don't have a proofer, so double check all of these for yourself - this is why I didn't just do this in the first place.) Here, you can just have fun. You're going to need about 86 inches of yardage (44 inches wide) at that point for the coins - 3ish yards total, which does make sense given that you're covering about a third of the quilt and you're losing a fair bit to seam allowances.
You've also got the sashing, which will end up needing to be 5.5" by 83", and you need 6 of them. The borders are going to be two sizes, two of 8.5x82.5, and two that are 8.5 x 83.5. So I'd get 2.5 yards of the border (This is cool, because it'll actually allow you to have the borders as a single piece, with not a huge amount of wastage (and you can always add any waste to the back or in with the coins.) You could get away with buying a bit less if you piece the borders, you're on your own for the math with that. For the sashing, you're going to need about the same, again, unless you want it pieced. If you want those pieced, then you're going to want a little over 2 - If you're worried about underbuying, just get 2.5 and call it done
For the coins, all this means about 14 fat quarters, but I'd pick up a couple more than that, just to make sure. If you don't want to get that many, you can increase the size of the borders and reduce the number of columns, but you're on your own for the math for that
- I wouldn't go more than 12" borders at any rate. By leaving such a wide border of batting around the top, this gives you the flexibility to be a half inch bigger in one dimension than in another, or not to have to worry about tiny measurements. I swear to god, fabric is a liquid, and it does things you never expect it to.
So, to sum up
You need the equivalent of about 14 fat quarters of fabric (or 3 and a half full yards, however you want to do it.) You'll have some left over, but you won't have to go *back*. You need 2.5 yards of the sashing fabric, and 2.5 yards of the border fabric.
For the back, pieced, you need about 6 yards. If you want it plain, then 3 yards of wide backing will do. And I really, really suggest double checking all my math. And if you're in the Golden Horseshoe area rather than on the west coast, PM me - I have some good sources for backing and border fabrics.