Calculating Quilt Fabric Yardage 101

Using a Rail Fence quilt as an example

by Julie Baird

This post contains affiliate links for which I receive compensation.

Learn to calculate quilt fabric yardage for a Rail Fence quilt design

A quilter, Lorraine G., recently asked for quilt fabric yardage requirements for a quilt she planned to make.

Specifically she wanted to know:

"How much fabric do I need for a Rail Fence in 3 colors and with 10" and 12" finished blocks.

Also, what are the cut width sizes for these.

I need a quilt that is about 90" square."

With only three unique patches (and all of the same size) to consider, this question provides the perfect example for learning to calculate yardage requirements.

There are two ways to do it.

In the first section we'll explore using quilt design software (EQ7) to figure it out.

Further down this page, we'll use paper, pencil and a calculator starting with a list of the orderly steps in the calculations and then going through our Rail Fence example with two different block design.  

Let's get started!

Using design software for fabric yardage calculations

Due to its limited fabric palette, strip piecing is the most efficient way to piece this quilt.

Using this technique means each strip's width must be easy to cut with a rotary cutter and ruler—that means no 1/3" units since the majority of rotary rulers are labelled in 1/4" and 1/8" increments.

The only ruler I've ever seen with 1/3" increments is the Wonder Ruler, click here to learn about it.

To meet Lorraine's requirements and this cutting limitation, I drafted two different blocks into my Electric Quilt 7—a quilt design software for both the PC and Mac.

Option 1

Rail Fence quilt block for a zig zag pattern

In this first option (left), each 6-1/2"(unfinished) unit contains a unique patch from each of the three fabrics.

Four units are then stitched into a block that measures 12-1/2" unfinished (12" finished).

Using a straight set layout of 8 x 8 blocks, the finished patchwork measures 96-1/2" square including 1/4" binding, slightly above Lorraine's size requirement.

The patchwork design looks like this...

For the patchwork design above, the program returned these yardages:

  • Dark: 3-5/8 yds
  • Medium: 3-5/8 yds
  • Light: 3-5/8 yds

You will need additional fabric for binding. At this time (Feb. '14) these calculations are not available within the EQ7 program.

On this site, there are charts to help you determine the amount of binding you'll need based on the size of your quilt. Click here for that information.

Where to find the calculations in EQ7:

In the EQ7 program, from the 'Quilt Worktable', click the printer icon and then select 'Fabric Yardage' from the drop down menu. You have the option to choose the fabric width (remember this is the 'usable' width) from 5 preset values and then change the size of your seam allowance.

Once you've made these selections, then either print or preview the yardage requirements.

Option 2

In this second block option, the strips from these three fabrics are cut 1-1/2" wide.

Rail Fence quilt block for a woven effect

The 5-1/2" unfinished units contain 5 strips. Unlike Option 1 where each fabric is used just once, here the dark and medium fabrics are each used twice in each unit.

Four units are joined into a block measuring 10-1/2" unfinished (10" finished).

81 blocks are laid out in nine rows of 9 each. The finished patchwork measures 90-1/2" square including 1/4" binding.

The fabrics required as calculated in the EQ7 program are:

  • Dark: 4-5/8 yds
  • Medium: 4-5/8 yds
  • Light: 2-5/8 yds

As before, you'll need additional fabric for binding.

The design looks like this...

Swap the position and yardage for just the light and dark fabrics and the patchwork design morphs into this...

The choice is yours!

In drafting this design, it became quite apparent that there must be a distinct difference in the values of the light, medium and dark fabrics. Otherwise the design gets really smushy and almost disappears. (Click here to see what I mean!)

What if you don't have the EQ7 software?

Never fear! There's ALWAYS more than one way to get things done in quilting. The trick is finding what works best for YOU and what best fits your budget.

To compute the needed quilt fabric yardage, you'll need paper, pencil and  a calculator (if you don't care to do the math in your head).

You'll need to have a quilt design with all of it's unique patches identified and sized.

Let's get started!

Simple steps for manually figuring quilt fabric yardage

To determine how much fabric is needed to make a quilt, we compute the amounts needed for each unique patch in the design using the following steps:

  • Identify the unique patches in the design.
  • Determine how many of a unique patch can be cut from the usable width of fabric.
  • How many strips will it take to get the required quantity of a unique patch.
  • Multiply the number of strips by the strip's width.
  • Add your personal 'insurance'. 
  • Record and label the result in an orderly fashion so it's easy to recall at a later date.

The Calculations

For both options, the blocks are strip pieced from fabric strips with a usable width of 40"

Block 1 Option

To review:

  • Blocks are 12" finished
  • 2-1/2" strips of each fabric are needed
  • Units are 6-1/2" square unfinished
  • Make 64 blocks
  • There are three unique patches—a light rectangle, a medium and a dark one

How many of the unique light patch are needed?

Simply count how many times the light patch appears in the block. In the diagram above there are 4.

Multiply this by the number of blocks that contain it:

4/block x 64 = 256 light patches

How many light patches can be cut from a width of fabric?

Each light patch is 2-1/2" x 6-1/2" where 6-1/2" is the unfinished length of a unit. The computation is:

40" strip ÷ 6.5" = 6.153

The decimals go on and on, but there's no need to go further than 3 places.

Since we can't piece with partial patches, round down to get 6 unique light patches from one strip.

How many strips are needed?

Simply do the math.

256 patches ÷ 6 patches/strip = 42.666 strips

This time round up because we use full strips, so it takes a total of 43 strips to cut 256 light rectangles.

How much fabric is needed without insurance?

Remember our strips are 2-1/2" wide. Determine the number of inches needed by multiplying:

43 strips x 2.5" = 107.5 inches

To convert to yardage divide by 36":

107.5" ÷ 36" = 2.986 yards

Round up to a number your local quilt store will be happy to cut or 3 yards.

Determine your 'insurance'.

Insurance will differ from quilter-to-quilter and patch-to-patch.

EQ7 calculated 3-5/8 yards of a light is needed. The program added an additional 5/8 yds or 22-1/2" extra.

Only you can decide if that is right for you. Some of the things that whittle away at the extra inches include:

  • Fabric shrinkage if you prewash (it tends to shrink more on the crosswise grain and you may not get as many patches from each strip after washing)
  • Squaring up after several of cuts
  • Fewer patches can be cut from strips cut crooked at the fold
  • Miscuts
  • Using a fabric cutting machine like an Accuquilt

For this quilt, 5/8 yard looks like a fair amount. Any leftovers can be used in a scrap quilt later.

Since each unique patch is identical in size, the quilt fabric yardage for the medium and dark fabrics is also equal to 3 yards PLUS your insurance amount.

Block 2 Option

To calculate the quilt fabric yardage for our Option 2 block, follow the same steps, noting that:

  • Blocks are 10" finished
  • 1-1/2" wide strips are needed
  • The units are 5-1/2" square unfinished
  • Make 81 blocks

Plugging in these values for the dark or medium fabrics:

8/block x 81 blocks = 648 patches

40"/strip ÷ 5.5"/unit = 7.272 or 7/strip

648 patches ÷ 7/strip = 92.571 or 93 strips

93 x 1.5"(strip-width) = 139.5"

139.5" ÷ 36" = 3.875 or

3-7/8 yards each of a dark and a medium PLUS your insurance

Repeat the process for the light:

4/block x 81 blocks = 324 patches

40"/strip ÷ 5.5"/unit = 7.272 or 7/strip

324 patches ÷ 7/strip = 46.285 or 47 strips

47 x 1.5" = 70.5"

70.5" ÷ 36" = 1.958 rounded up to 2 yards PLUS your insurance

A note about 'usable width' and strip piecing...

The strip piecing technique adds an extra 'twist' on the quilt fabric yardage  calculations.

If all the rectangles are cut and stitched individually, then it doesn't make any difference if the yardage is of different widths—simply do the computations for each unique patch from each unique fabric.

With strip piecing, the fabric-strips are sewn together, pressed and then cut into units/patches. If there are several different usable widths, then use the narrowest measurement for the calculations for each fabric used in the strip set.

You can easily see how a narrower width could possibly effect the number of patches able to be cut from each set.

If you enjoyed this article and found it helpful, please let me know by clicking this button - thank you!

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