Quilt Math: Know your ruler!

Know Your Ruler (and a couple of other measurements)

This may be so basic to some people it’s laughable; however, there are a number of people out there to whom this will be very helpful.

Until I started quilting, I was scared to death of a ruler. I guess I inherited my fear of math from my mother (who is totally on my side and “doesn’t get it” either). However, once I learned my way around a ruler, it’s not very hard to figure out at all.

Most acrylic quilting rulers are marked in 1/8” increments. (There may be some 1/16” quilting rulers out there, but I haven’t seen one.) Each small tick mark on the ruler represents 1/8”. The medium tick marks indicate ¼” and the largest marks are one inch indicators. The marks go like this: 0, 1/8, (2/8) ¼, 3/8, (4/8) ½ , 5/8, (6/8) ¾, 7/8, (8/8) 1.

Measurements on a yard stick are similar. A yard stick measures 36” long. Therefore ½ a yard is 18”. How many inches make up the following measurements:
3/8 of a yard? __________
1/4 of a yard? __________
1/8 of a yard? __________
5/8 of a yard? __________
7/8 of a yard? __________
¾ of a yard? __________

If you’re not sure, here’s how to figure it out: divide 36” by the bottom number (in the case of 3/8 a yard, 36/8 = 4.5). Then multiply the result by the top number (4.5 x 3 = 13.5 inches).

Other Measurements You’ll find in Quilting:
From selvage to selvage, most quilting fabrics are 42” – 44” wide
Fat quarters are typically 18” x 21” cuts of fabric (twice as wide, but half as long as a ¼ yard piece of fabric that has been cut from selvage to selvage).

Skill Builder
Requirements: rotary cutter, self-healing mat, acrylic ruler, one 6-1/2” square of scrap fabric, five scraps of fabric at least 17” long
1. Cut strips of of fabric into the following increments:
1-3/8 x 17
1 x 17
2-3/4 x 17
2 x 17
1-7/8 x 17

3. Using a ¼” seam, sew the strips together. Press all seams to one side.

Test: How big should the strips be when they’re sewn together? (figure it out before sewing and measuring. Hint: remember to account for the ¼” seam!).

4. Cut the resulting layers into six 2-1/2” chunks.

5. Sew two chunks together. Repeat one more time so that you have 2 long chunks and 2 short chunks.

6. Sew one of the short 2-1/2” chunks to one side of the 6-1/2” square (the chunk will be longer than the square so just trim off the excess). Repeat, sewing the other short 2-1/2” chunk on the other side of the square and trimming the excess. Press the seams to one side.

7. Sew one of the longer 2-1/2” chunks to the third side, again, trimming off the excess. Repeat on the 4th side.

Test: How large should the resulting block be?

Answers:
3/8 of a yard? 13.5" (36 / 8 * 3 = 13.5)
1/4 of a yard? 9" (36 / 4 )
1/8 of a yard? 4.5" (36 / 8)
5/8 of a yard? 22.5" (36 / 8 * 5)
7/8 of a yard? 31.5" (36 / 8 * 7)
¾ of a yard? 27" (36 / 4 * 3)

How big should the strips be when sewn together? 7”
Subtract 1/2" for each inner piece and 1/4"* for the two end pieces:
1 3/8 - 1/4* = 1 1/8
1 1/2 - 1/2 = 1/2
2 - 1/2 = 1 1/2
1 7/8 - 1/2 = 1 5/8
2 3/4 - 1/4* = 2 1/4

Next convert each increment to 1/8" fractions:
1 1/8 = 1 1/8
1/2 = 4/8
1 1/2 = 1 4/8
1 5/8 = 1 5/8
2 1/4 = 2 2/8
Total: 5 16/8 = 7

How big should the resulting block be? 10-1/2”
2 1/2 - 1/4* = 2 1/4
6 1/2 - 1/2 = 6
2 1/2 - 1/4* = 2 1/4
Total: 10 1/2"

*only 1/4" because the other side of the seam hasn't been sewn yet.