Mathematically Challenged...
 

And, I can't "conceptualize" either.

Maybe someone can help.

I need a backing for a quilt and the backing needs to be 80" by 56". I want the seam to run horizontally, across the width of the quilt, not vertically, along the length.

How much fabric, at a regular 45" do I need to buy?


Thanks, Watson

Try looking at some of the backing material at Marshall Dry Goods. Backings come in 90 and 108 wide, so a couple of yards will do. No seams.

My method. Most fabrics have usable about 40 inches wide. Most times it doesn't matter whether you do WOF or LOF.

So divide 80/40 = 2 widths to make your length.
2 widths x 56 inches = 112 inches total length of fabric
112 inches divided by 36 inches in a yard = 3 yds (108 inches) + 4 inches = 3.11 Yds.
Round the .11 up 1/8 (4.25") or 1/4 (9 inches)

Edited to add: When I make my backings like this, I use a 1/2 inch seam allowance and iron the seam open. This takes most of the bulk out of the seam.

Using Barb's calculations, I'd buy 3.5 yards. It might shrink a little when you launder it before use and you need extra on the ends - I like at least 2 inches (4 inches for 2 ends) , sometimes 3 (6). With a longarm, you might need more. (Remember to double the amount you allow for each end). 3.5 yards = 126". You need 112 + 1 for seam + 6 for ends=119", so 3.5 yards doesn't too allow much for shrinkage.

For starters, I would also "assume" that the fabric only had 40 inches usable width.

Are you planning to have it long-armed? How much "extra" will you need?

If I was doing the backing and needed 5-inches extra all around, I would buy 5-2/3 yards of fabric and would have leftovers.

I would also wash it before cutting it.

But I just checked - and you live in Canada where fabric is more expensive (usually) than in the USA.

I don't remember if you are in the wash before cutting group or not -

Anyway - I have found some fabrics have shrunk over two inches in width - some have shrunk over two inches in length - very very few that have not shrunk at all.

I also would choose a wider backing. Would save money in the long run. There is a lot of 90" and even 118" at reasonable prices.

I agree that the wider backing would be easier - and probably less expensive, in the long run.

Cotton sheets from the thrift store...no seams and less $$$.

I use the Robert Kaufman quilt calculator app. It gives yardage for both vertical and horizontal piecing.

Thanks everyone.

I had already figured in the extra for long-arming, so I'm OK that way. I bought everything they had....3.7m, so that's just over 4 yards.

Thanks, again!

Watson