Quilting,  Sewing,  Tutorials

How to Calculate How Much Fabric You Need for a Simple Quilt

When I used to work at a fabric store, the most common question I received was this: “I’m making X, so how much do I need?” If you’re not following a pattern, you can get overwhelmed with the fabric measurements and either over buy or shortchange yourself. Either way, it’s unhappy for your bank account and your sanity.

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This article will guide you through the process of calculating how much fabric you will require for a quilt made with easy square blocks.

How big is your quilt going to be?

Crib size? Lap quilt? Table topper? California King? There are no rules when it comes to how large you want to go, as long as you’ve got the batting and the courage.

What you need to know:

  • What will your final dimensions be?
  • How big would you like your squares to be?

The size of the squares you cut out must be slightly larger than the finished size to account for seam allowance. For example, if you want your finished blocks to be 5″ by 5″, you will need to cut out squares of 5.5″ by 5.5″ to account for a quarter-inch seam allowance on each side of the block.

Let’s say that we want to create a 50″ x 60″ lap quilt with 5″ squares.

How many blocks will you need to cut out in total?

To figure out how many squares will fit into each row, divide the finished quilt width by the block size (60 divided by 5 = 12 blocks wide).

To figure out how many squares will fit into each column, divide the finished quilt height by the block size (50 divided by 5 = 10 blocks tall).

Sometimes I like to draw a little picture to help me visualize it. (I did it in Photoshop here because it’s easier to see, but usually it would be an ugly not-to-scale sketch on the back of a phone bill.)

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Multiply the number of blocks in your rows by the number of blocks in your columns. In this example, we are multiplying 10 by 12 to discover we need to cut out 120 blocks total.

How many blocks do I need to cut out of each fabric in my design?

You can use as few or as many different fabrics as you’d like. When you are laying out your blocks in a random pattern, you can get a general idea of how many blocks of each fabric you’ll need to cut out by dividing your total blocks amount by the number of fabrics you’ve chosen.

So if you are using 7 fabric prints, you would divide 120 total blocks by 7. This works out to approximately 17.14. When your math does not work out to an even number, always round up to the nearest whole number (in our case, 18 squares from each fabric). If you round down, you will be short at least one block in the end! You’re better off to have a few extras than to be short.

If you are laying out your blocks in a specific pattern, I like to take my handy-dandy sketch and plan it out. I choose a coloured pencil or pattern to represent each fabric, then plot it out on the grid. In the end, you would have something like this:

Once all your blocks are accounted for, you would simply count up how many blocks you’ll require for each fabric. I have 10 forest green squares, 13 baby blue squares, etc.

How much fabric will I need to cut out X amount of squares?

There’s only a bit of math left, I promise. Now, we need to calculate how many blocks you can get out of one width of fabric. The key variable we need to know is the width of the fabric, not including the unusable selvage edge. Measure from one selvage to the other to find out how wide your fabric is. (Most quilting cotton fabric is 45″/110cm, but often the usable width is around 43″-44″.)

The next critical ingredient is your block size. Remember, you need to take your finished block size (ex: 5″x5″) and add a quarter-inch seam allowance to each side. A 5″x”5 square requires the fabric to be cut to 5.5″x5.5″.

Step 1:

This tutorial is assuming you are making square blocks. If you are making rectangles, you will have to decide whether you want to use your width or your height here, and then you’ll use the other number for step three.

Take your width and divide it by your cut-block size.

If your fabric is 44″ wide, divide 44″ by 5.5″ to discover you can fit 8 blocks in the width of your fabric. If your math ends up not being a whole number (ex 7.8), you will have to round down (ex: 7).

Step 2:

Now take the total number of blocks you need for that particular fabric and divide it by number of blocks you can fit in the width. If I need 18 blocks total, I divide that by 8. That results in 2.25. Round that number up to the nearest whole number (3) to discover that we need to cut three strips of fabric to have enough blocks.

Step 3:

Remember, if you are doing a specific pattern, you will need to do these calculations for each fabric. If you are doing an even distribution, you’ll just have to do these calculations once.

Multiply the number of strips required by the width of block. In our example, this would by 5.5″ times by 3 strips = 16.5″ of fabric.

Thus, in order to cut 18 5.5″ squares out of 45″-wide quilting cotton, we will require 16.5″ (almost half a yard) of fabric measured along the selvage edge.

Now that we know how many strips of fabric we’ll require for each fabric, it’s time to get cutting!

Cutting the Square Blocks

Take your first fabric choice and fold it lengthwise. Your two selvage edges (the machine-made edges, not the cut edges) should be together.

I truly recommend investing in a rotary cutter and cutting mat. It makes the whole process of cutting fabrics so much easier. I honestly could not go back to using scissors and fabric pens to mark out squares!

Be sure to square up the raw end of your fabric. If you have a rotary cutter, ruler, and cutting mat, this task will be very easy. Just make sure that your fabric is lined up with the guidelines on your mat, and cut a straight line from selvage to folded edge.

Once you’re squared up, move your ruler down one-width of your blocks. In the case of our example, move your ruler down 5.5″ inches and make a cut parallel to your initial cut. Repeat until you have the amount of strips you calculated.

Once your strips are cut out, cut off the selvage edges. Unfold the strips and cut them at 5.5″ (or however wide your blocks are) intervals.

Cutting out squares is relaxing once you know how much fabric you’ll require for each fabric in advance. It’s much easier to adapt to fabric shortages when you know before you start cutting where you will account for extra squares. (Ex: I only have enough fabric for 16 squares, so I’ll account for 2 extras from another fabric to make up for it) It looks like a lot of steps, but the math is easy. Go for it!

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