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Fat eighths are 9″ x 21″ rectangle cuts of fabric that are very popular among quilters. The term “fat eighth” is in reference to the way the eighth yard of fabric is cut.
A regular eighth yard of fabric is cut into a long 4.5″ x 42″ strip, but a fat eighth is an eighth yard of fabric cut in a 9″ x 21″ rectangle. Rather than the yard being cut into 8 strips, it’s cut into 8 rectangles. This allows for larger pieces to be cut from the piece of fabric.
Fat eighths are typically sold in curated fat eighth bundles. There is no standard number of fat eighths in a bundle, so you can expect to find bundles of anywhere from 12 to 40 fat eighths.
Fat eighths are popular among quilters because they are sold in curated bundles which takes the guesswork out of choosing fabric for a quilt. Quilts made from fat eighth bundles have a scrappy look but are still cohesive. Fat eighths are also a great way to build up your fabric stash if you are new to quilting.
But how do you determine how many fat eighths you’ll need for your project? Let’s find out.
Before you can determine how many fat eighths you’ll need for a project, you’ll need to figure out how large your quilt will be. If the quilt you’re making is meant for a bed, you can use the mattress size. Remember to add several inches if you want the quilt to hang off of the bed.
Check out my free printable quilt size chart if you need a refresher on quilt sizes!
If your quilt is not meant for a bed, you can be more flexible with your measurements and use some of the suggested sizes that I have listed in my examples below.
After you know your desired quilt size, you can calculate how many fat eighths you need for your quilt, or you can use my example calculations to get a general idea of how many you’ll need.
My example calculations are using full 9″ x 21″ fat eighths (minus ¼” seam allowance on all sides). After removing 1/2″ for the seam allowances, the finished rectangle size will be 8.5″ x 20.5″.
My calculations do not account for pieced blocks, sashing, or borders. If you want to cut into your fat eighths, add sashing, or add borders, you’ll need to adjust these calculations.
Please use my calculations for reference only, and be sure to double-check your quilt math before you go shopping for fabric!
Want to save this information for later? Download this FREE Fat Eighths in a Quilt Cheat Sheet! The cheat sheet includes the math for fat eighths oriented both vertically and horizontally.
How Many Fat Eighths Does it Take to Make a Baby Quilt?
In order to make a 34” x 41” baby quilt, you will need 8 fat eighths arranged vertically in a 4 x 2 grid.
You can make a 41″ x 42.5″ baby quilt with 10 fat eighths arranged horizontally in a 2 x 5 grid.
Keeping the fat eighths in one piece is a great way to highlight large print fabric or make a quick and easy baby quilt.
How Many Fat Eighths Does it Take to Make a Throw Size Quilt?
To make a 51” x 61.5” throw quilt, you will need 18 fat eighths arranged vertically in a 6 x 3 grid.
You can make a 61.5″ x 68″ throw quilt with 24 fat eighths arranged horizontally in a 3 x 8 grid.
How Many Fat Eighths Does it Take to Make a Twin Size Quilt?
To make a 68” x 82” twin size quilt, you will need 32 fat eighths arranged vertically in a 8 x 4 grid.
You can make a 61.5″ x 76.5″ twin quilt with 27 fat eighths arranged horizontally in a 3 x 9 grid.
How Many Fat Eighths Does it Take to Make a Full Size Quilt?
To make an 85” x 102.5” full size quilt, you will need 50 fat eighths arranged vertically in a 10 x 5 grid.
You can make an 82″ x 93.5″ full size quilt with 44 fat eighths arranged horizontally in a 4 x 11 grid.
How Many Fat Eighths Does it Take to Make a Queen Size Quilt?
To make a 93.5” x 102.5” queen size quilt, you will need 55 fat eighths arranged vertically in a 11 x 5 grid.
You can make an 82″ x 102″ queen quilt with 48 fat eighths arranged horizontally in a 4 x 12 grid.
How Many Fat Eighths Does it Take to Make a King Size Quilt?
To make a 102” x 102.5” king size quilt, you will need 60 fat eighths arranged vertically in a 12 x 5 grid.
You can make a 102.5″ x 102″ baby quilt with 60 fat eighths arranged horizontally in a 5 x 12 grid.
How to Calculate How Many Fat Eighths Are Needed For a Quilt
If you want to do your own math, here’s how to do it.
Before we do any calculations we need to subtract the seam allowance from our fabric. The standard seam allowance for quilting is ¼ inch. Because there will be seams on every side of our fat eighth, we need to subtract two seam allowances from our starting measurement of 9″ x 21″. That leaves us with a finished rectangle size of 8.5″ x 20.5″.
Now that we have the size of our fat eighth blocks, we can divide our finished quilt dimensions by 8.5″ x 20.5”.
Let’s do a quick example where the fat eighths are arranged vertically:
We want to make a baby quilt. According to these quilt size guidelines, a good baby size quilt is 30″ x 40″. We’ll base our measurements on that guideline.
To determine the number of fat eighths needed we’ll divide 30” / 8.5” to get 3.52. Because we don’t want a partial square, we’ll round that up to 4. We will need 4 fat eighths to reach our quilt width of roughly 30”. The width will technically be 34″ (4 x 8.5).
Now let’s do the length. We’ll divide 40” x 20.5” to get 1.9. Again, we’ll round up to 2. We will need 2 fat eighths to give us a roughly 40″ quilt length (41″ to be exact).
Now we’ll multiply the number of squares together. 4 x 2 = 8 fat eighths. For a 34″ x 41″ quilt we need 8 fat eighths.
HELPFUL TIP: When calculating how many fat eighths you need for a quilt be sure to account for any sashing or borders you may want to add. For example, if you want a 4-inch border around your quilt, subtract your desired quilt size by 8” to account for your borders BEFORE you calculate how many fat eighths you need.
Fat Eighth Quilt Size Charts
Below is a chart that shows the largest quilt you can make with 9″ x 21″ fat eighths oriented vertically.
|Number of Fat Eighths||Grid Layout||Largest Quilt Size|
|8||4×2||34″ x 41″|
|15||5×3||42.5″ x 61.5″|
|18||6×3||51″ x 61.5″|
|21||7×3||59.5″ x 61.5″|
|24||6×4||51″ x 82″|
|28||7×4||59.5″ x 82″|
|32||8×4||68″ x 82″|
|36||9×4||76.5″ x 82″|
|35||7×5||59.5″ x 102.5″|
|40||8×5||68″ x 102.5″|
|45||9×5||76.5″ x 102.5″|
|50||10×5||85″ x 102.5″|
|55||11×5||93.5″ x 102.5″|
|60||12×5||102″ x 102.5″|
Below is a chart that shows the largest quilt you can make with 9″ x 21″ fat eighths oriented horizontally.
|Number of Fat Eighths||Grid Layout||Largest Quilt Size|
|10||2×5||41″ x 42.5″|
|12||2×6||41″ x 51″|
|14||2×7||41″ x 59.5″|
|16||2×8||41″ x 68″|
|24||3×8||61.5″ x 68″|
|27||3×9||61.5″ x 76.5″|
|30||3×10||61.5″ x 85″|
|33||3×11||61.5″ x 93.5″|
|40||4×10||82″ x 85″|
|44||4×11||82″ x 93.5″|
|48||4×12||82″ x 102″|
|52||4×13||82″ x 110.5″|
|60||5×12||102.5″ x 102″|
|65||5×13||102.5″ x 110.5″|
Now you know how to figure out exactly how many fat eighths you need to make your next quilt. Grab a fat eighth bundle and get started! Remember to download the free cheat sheet so you can save this information for later!
Other Blog Posts You May Like:
How to Cut a Fat Eighth into Squares and Strips
How Many Fat Quarters Do I Need to Make a Quilt?
How to Cut a Fat Quarter into Squares and Strips
How Many 10″ Squares Do I Need to Make a Quilt?
How to Cut a Layer Cake into Squares and Strips
How Many 5″ Squares Do I Need to Make a Quilt?