Friday, December 11, 2009

Quilt Math

Math is a huge part of quilting, like it or not. I enjoy math, but somedays my thinking is a little too rough and the "brain on meds" doesn't work the way it used too. So to help out I utilize many tools. Several days of pondering the issue, with the known quilt formulas and assessing it with common sense. Drawing it out on paper to make sure I'll have enough fabric to do the quilt (this step is major, since my projects have a tendancy to grow before they are done! LOL ) Ask myself the same questions about a porject that I have on my focal point, check with any references online that can assist me and once in awhile give a shout out to one of the many friends in cyber land to verify my mathematics and thinking.

So when reading one of my favorite blogs I saw this topic and thought, WOW! great idea. Crazy mom quilts has many beautiful quilts and gives quick brief instructions. I'll paraphrase her directions and edit them along the way. ;~)

I'd like to list some basic quilt sizes:

A nice baby size quilt is around 42" x 52".
For a square baby quilt, anywhere from 36" to 42" works well.
A crib quilt measures 45" x 60".
A nice lap size quilt is 60" x 72".
Twin size, 63" x 88".
Full size, 78" x 88".
Queen, 84" x 92"
King, 100" x 92" or larger.

If you are making a quilt for a specific bed in your house, it's best to measure the top of your mattress and add the amount of overhang you want on each side, then you will have the perfect measurements for your bed. I'd recommend this, especially if you have a very deep mattress, or if you have head and foot boards to deal with. Or bunk beds.

These are target sizes. If your block calculations don't work out quite right, just round up.

So the numbers necessary for a twin size quilt:

A charm square=5".
Take away 1/2" (for seam allowances) and your finished square will equal 4.5".

63" (width of quilt) divided by 4.5" (finished square)=14
88" (length of quilt) divided by 4.5" (finished square)=19.56, which would round up to 20.

So 14 x 20=280 charm squares. Your layout will be 14 blocks wide by 20 blocks long. The quilt will measure 63" x 90".

This quilt was made by crazymom quilts. She had a nine patch a day challenge I started this past summer and mine is now in the UFO project pile, look at hers isn't it Pretty? I'll have to drag mine back to the front. I plan on making a quilt with D9P blocks on point with sashes, cornerstones and borders. Just recently I picked up 2 fabrics that will work for the borders and sashing, I'll have to lay it out to be sure.

For the 9 patch quilt based on a 6" finished nine patch:

The finished quilt measures 66" x 90" for the twin size. Each 9 patch block finishes at 6" and each sashing strip finishes at 2".

Since you want the quilt to be at least 78" wide, you will need 12 extra inches. You would need 20 extra blocks (ten for each additional column) and then add in the sashing 2" finished x 2 strips. The width of the twin quilt is 66" +12" (for the two extra columns of 9 patches) + 4" (for the two extra strips of sashing) =82", which is a bit wider than your target of 78", but close enough. Plus, it's nice to have it a bit too large than a bit too small. So the number of 9 patches needed would be 70 (from the original pattern) +20 = 90 for a full size quilt.

Now, a queen sized stacked coins quilt using this tutorial. It's the same tutorial I used for the baby doll blanket from this post but of course way smaller!

Your target size is 84" x 92".
Coins are cut 2.5" x 5", which will finish at 2" x 4.5".
The sashing is cut at 3.5", which will finish at 3".

The width of the quilt:
11 columns of coins x 4.5" (finished width)=49.5"
12 columns of sashing x 3" (finished width)=36".
49.5" (total coin width) + 36" (total sashing width)=85.5" wide. Perfect.

The length of the quilt:
This one will be worked backwards. You want it to be 92" long. Subtract 6", for the top and bottom sashing, which will give you 86".
86" divided by 2" (finished height of each coin) =43.
So 43 coins in each column x 11 columns= 473 coins.

473 divided by 2 (number of coins that are cut from a charm pack)=236.5, which would be rounded up to 237 charm squares required.
If there are 40 charms in a pack, you would need 6 packs of charms.

For the yardage needed for sashing, you will need 12 strips that are cut 3.5" x 86" and 2 strips that are cut 3.5" x 85.5". For this step, I'd enter those numbers into the handy dandy quilt calculator (someone had directed to me awhile back, thanks to whomever did so, it's so very wonderful!) which will tell me that:
for the 12 strips that measure 3.5" x 86"= 2.5 yards
for the 2 strips that measure 3.5" x 85.5"=2.375 yards
for a total of 4.88 yards, to which I would just round up to 5 yards.

Remember when calculating to use your FINISHED block size, not your CUT size, or you will have a quilt that will be much smaller than you want.

Happy Stitching,

Adding this link to quilter's paradise about how much fabric to buy for borders. It allows and calculateshow much fabric for up to 5 borders on a quilt.

Many free patterns are on this link

Set in triangles math at Lyn Brown's.

The blog for sew many ways link is here which has many tool time tips and organizing.

Heather Thomas has a tutorial for piped bindings shown well here.

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