How to Make a Quilt Finish at a Certain Size

Problem: I want to make a quilt a certain size. How do I account for shrinkage from quilting?

Today’s bed mattresses are thicker than ever. If a relative wants you to make them a quilt “of a certain size” such as from the bottom of one side of the mattress to the bottom of other side, how much bigger do you need to make the quilt top in order to meet the size requirement once it is quilted, bound, washed and dried?

I decided to make some small samples in order to test possible answers to this question.

First, I tested for difference in the quilting density. I cut 3 tops, all 9 x 20 inches, of unwashed 60 square good quality quilter’s cottons. I layered each of them with cotton batting size 10 x 21 inches (Color Me Cotton from Air Lite 100% cotton with scrim) and backing size 11 x 22 and quilted them at three different densities. I measured them after binding and also after washing and drying. Here is a chart of my findings:

Samples quilted in three different densities

With a 2 inch difference in a 20 inch sample, that means if I want a quilt to finish at 90 x 90 inches, I would have to make it 100 x 100 inches to allow for shrinkage from quilting and washing/drying. (Typically I am not a pre-washer, but this test makes me want to prewash my fabrics for the top and the backing.)

I also repeated this same 3 examples using two layers of batting. There were essentially no differences in the samples.

Next, using one yard of the same fabric, I drew a rectangle 9 x 20 inches along the length of grain (selvedge) and another rectangle along the width of grain. I washed the yard of fabric along with a yard of the batting that I also had drawn a rectangle on. It is not recommended to prewash batting, but I wanted to determine if the shrinkage was what the manufacturer predicted, which was 1 percent.

After washing, the fabric along the width of grain had shrunk to 8⅞ x 18⅞. Along the length of grain, it shrank less to 9 x 19½. The batting shrinkage was about ⅛ of an inch on the long side and none on the shorter side.

I cut another 9 x 20 inch rectangle out of the prewashed fabrics and quilted them at 1½ inch grid. I used the same fabric for the backing and did not prewash the batting. After binding, washing and drying, this piece measured 8½ x 19 inches.

Conclusions:

Prewashing the fabric will reduce the amount of shrinkage that happens to your overall quilt. However, it does not take in to consideration the shrinkage that happens with quilting and washing the entire project. There is a “marrying” of the fibers when all the fibers are cotton that bind the quilt together. This takes up some of the width and length of the quilt in the overall measurements.

Recommendations: The only way to predict how your project is going to react to quilting and washing is to do your own test samples. Because greige goods vary from manufacturer to manufacturer and batting varies from company to company, making broad statements is not possible. The fabric I used was from Henry Glass. It was of excellent quality, but even within the company (which has their fabric primarily printed in Korea) the printer can use different greige goods from line to line so there is no possible way to completely predict outcomes without testing the exact fabrics which are to be used in your project.

I don’t think it is necessary to make a full size quilt, but making a 9 x 20 piece (you will get two from a fat quarter) and using the same backing as you plan to use is a good start. Naturally, you will need to use the exact same batting to get results that are predictable. Remember that even 1/8 of an inch difference in your little sample piece will be duplicated to 1 inch across the quilt if it is 100 inches in size.

For example, if you need your quilt to finish at 115 x 115 and your sample shrank after prewashing, quilting, binding, washing and drying from 20 inches to 19 inches, you would make your top 121 x 121 inches and wash and dry it before gifting it.

Was this a helpful article? Please let me know if making a test sample is helpful for you to have a quilt finish at the right measurement.