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Although quilting is one of the most creative and fun things you can do, sometimes
it is necessary to make mathematical calculations, especially if you like to design
your own patterns. Listed on this page is some useful information that can be
referred to when you are feeling math challenged.
Yardage
Measurements Fabric
is usually purchased "by the yard", 36 inches, or a fraction of a yard.
Fabric is traditionally manufactured in 44" widths; however, recently some
manufacturers have shortened that to 42". These measurements explain what
the length of the fabric cut is when you buy a fraction of a yard.
| Yardage | 1/8 | 1/4
| 3/8
| 1/3
| 1/2
| 5/8
| 2/3
|
3/4 |
7/8 |
1 | | Inches | 4.5
| 9
| 13.5
| 12
| 18
| 22.5
| 24 | 27
| 31.5
| 36 |
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Fat
Quarters
Normally
1/4 of a yard of fabric would be a piece that measured 9" x 44". Quilters
use a special cut of fabric called a "fat quarter". It results in the
same area of fabric, but the yardage has been cut differently so that the piece
measures 18' x 22", enabling quilters to cut larger pieces than you could
from a regular quarter of a yard of fabric.
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Quilt
Dimensions
There
are variations in what determines the appropriate size for a bed quilt. When determining
how big you want your quilt to be, you must first know the dimensions of your
mattress. These are listed below.
- Standard
Mattress Sizes
Crib Mattress: 28" x 52" Twin/ Single
Mattress: 39" x 75" Full/ Double Mattress: 54" x 75"
Queen Size Mattress: 60" x 80" King Mattress: 76" x 80"
California King: 72" x 84" Next
you must know how far you want the quilt to come down on the side of the bed.
This is called the "drop". A quilt needs at least a 12" drop on
each side and the bottom if you want it to cover the side of the mattress and
you need to add an additional 15" to the top edge if you want to cover the
pillow. If you want the quilt to serve as a full-size bedspread with a 21"
drop on each side, the chart below lists common sizes.
| Twin
/ Single | Full
/ Double | Queen | King | | 81"
x 110" | 96"
x 110" | 102"
x 115 | 120"
x 115 |
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On Point BlocksBlocks
that are arranged "on point" are rotated so that the square block is
laid out in a diamond effect. While this is a beautiful layout, it creates some
mathematical complications when designing a quilt. This is because the diagonal
measurement of the block is creating the width. To determine this measurement,
you simply multiply the finished block size by 1.41. For example, 6" square
block no longer has a 6" width on the quilt top, but has a width of 8 1/2".
The chart below gives diagonal measurements for a number of common block sizes.
| Finished
Block Size | 1" | 2" | 3" | 4" | 5" | 6" | 8" | 10" | | Diagonal
Measurement | 1-1/2" | 2-7/8" | 4-1/4 | 5-5/8"
| 7-1/8" | 8-1/2
" | 11-
3/8" | 14-1/8" |
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Decimal
Conversation
Sometimes
quilt making requires that we cut pieces with strange, fractional measurements.
Knowing the fractional equivalent in decimals can be a help. The following chart
provides decimal equivalents for a number of common fractions used in cutting
quilt pieces. | Fraction | 1/8 | 1/4 | 3/8 | 1/2 | 5/8 | 3/4 | 7/8 | 1 | | Decimal | .125 | .25 | .375 | .50 | .625 | .75 | .875 | 1.0 |
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Corner
Setting Triangles Corner
setting squares are made from half square triangles. That means that a square
block has been cut on the diagonal, resulting in two triangles. The legs of the
triangle form the outside edge of the quilt and the hypotenuse is sewn to the
block edge. There are two formulas that can be used to make corner setting triangles.
Formula #1 has you divide the finished block size by 1.414; then add .875
for the seams, and round up to the nearest 1/8". The square block would be
cut this size and then cut corner to corner with one diagonal cut, resulting in
two corner triangles.
Formula #2 has you multiply the finished block size
by 1.41 and divide that answer by 2. Then add .875 for seams and round up to the
nearest 1/8". Cut a square block this size and then make one diagonal cut,
corner to corner, resulting in two corner triangles.
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Side
Setting Triangles Side
setting triangles are used along the side a quilt with on-point block layout.
They are made by cutting a square twice diagonally, resulting in 4 triangles.
The legs of the triangles are on the bias and the base is on the straight of grain,
thus it goes on the outside of the quilt top.
The formula for figuring
side setting triangles is to multiply the finished block size by 1.414, add 1.25
to this measurement, and then round up to the nearest 1/8". This is the size
to cut the square block, which will then by crosscut diagonally twice, resulting
in 4 triangles.
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Common
Setting Triangle Sizes This
chart lists the sizes of squares that will be cross cut to create setting triangles.
Finished
Block Size | Side
Triangle Squares | Corner
Triangle Squares | 4" | 7" | 3-3/4" | 5" | 8-3/8" | 4-1/2" | 6" | 9-3/4" | 5-1/8" | 7" | 11-1/4" | 5-7/8" | 8" | 12-5/8" | 6-5/8" | 9" | 14" | 7-1/4" | 10" | 15-1/2" | 8" | 12" | 18-1/4" | 9-3/8" | 14" | 21" | 10-3/4" |
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