How to Adjust a Quilt Block Size

How to Adjust a Quilt Block Size takes a quilt block as written in the pattern and gives tools and skills to adjust the block to make it either larger or smaller.

This is a Blitz Quilt.  Actually these are several Blitz Quilts.  I have yet to find a color combo that I don’t want to make this quilt in.

And this is a Modified Blitz Quilt, where the blocks are much smaller than the original.

Why Adjust a Quilt Block Size?

There are lots of reasons that a quilter might wish to adjust a quilt block size. 

Sometimes I’ll adjust the quilt block size just because I’m looking for a quilty math challenge.  And by “looking for a challenge” I don’t mean a “tear my hair out in frustration” sort of situation.  Rather, I like to stretch those mental math muscles. 

I know, I know.  I’m weird.

Sometimes, like this time, it’s helpful to have the ability to adjust a quilt block size because of fabric constraints, specifically, having pieces that are too small to make the pattern as written.

Making Scrappy Quilts

This extra scrappy baby quilt, for a dear friend’s new baby, started as a scrappy quilt for another dear friend.

This is the Diamond Twist Quilt, and making these blocks leads to some leftover Half Square Triangles. 

I just cannot throw away usable scraps, so I paired the Half Square Triangle scraps with the very large amount of similarly colored fabrics in my stash.

And this very sweet baby quilt is the result.

How to Adjust a Quilt Block Size

Now, for actual instructions on how to adjust a quilt block size.  These are going to be generic instructions that can be applied to nearly any quilt block you want to make.

This graphic shows both a finished quilt block (everything inside the black border), and the cut block size (the red border) before the seams have been sewn.

Now, do you notice that nowhere in that image does it give you sizing dimensions?  That was intentional!

No matter what size block you make, or how many little pieces go into making up the block, the seam allowance is always going to be the same ¼”. 

With the image above, for a 4” block, plus ¼” seam allowances, you would want to cut your fabric square at 4½”.  However, if you wanted to double your block size to 8”, you wouldn’t double your cutting size from 4½” to 9” because you don’t need to double your seam allowance.

So, for every quilt block that you want to make larger or smaller, you want to base your adjustments on the finished block size and then add in the seam allowance to get the cut size.

I know, I know, this tutorial is heavy on math, and you have learned from Darcy Quilts that I try to steer clear of too much math in most of my tutorials.  I’m sorry!

Let’s look at a couple of traditional quilt blocks with a whole bunch of graphics and hopefully that will make the yucky math clearer and easier to tackle.

Rail Fence Quilt Block Made Smaller

This is a rail fence quilt block.

Let’s say that this is an 8” quilt block.  When the quilt is all sewn together, each of those pink strips will measure 2” wide by 8” tall.  That means that before the pieces are sewn together, when they are the cut size, they will each measure 2½” wide (that’s 2” that shows in the quilt block + ¼” left seam allowance + ¼” right seam allowance) by 8½” tall (8” to show in the quilt block + ¼” top seam allowance + ¼” bottom seam allowance.).

What if you want to make a 4” block?

Each of the finished pink strips will measure 1” wide by 4” tall.  So, the cut size will be 1½” by 4½”.

You’ve just adjusted a quilt block size to make it smaller!  This is a very quickly made image of what a quilt made from this block might look like.

This is a Rail Fence Quilt, and if you like the look of this, you should check out this Rail Fence Tutorial which takes this basic block and offers lots of variations.

Churn Dash Quilt Block Made Larger

This is a traditional quilt block called Churn Dash.

This is what it might look like in color.  Like most traditional quilt blocks, there are a gazillion variations to consider, but for today, we’re going to focus on the most basic block.

I chose this block as the one to adjust a quilt block size LARGER because this block is made up of three components so it is a bit more complicated than the Rail Fence block.  Not enough additional complication to scare you away, but just enough to help you to envision how to adjust other quilt blocks you encounter, not just the ones specified here.

Each of the 9 pieces of this quilt block (separated by a red line) have their own seam allowance. They need to be taken individually when considering making the block larger or smaller.

Let’s start by thinking this is a 6” quilt block.  Each of those sections will then be 2” finished in the quilt block, and 2½” when considering the ¼” seam allowances around each side. 

What if we double the block to be 12”?  Each of those components would be 4” when finished and 4½” unfinished. 

What if we settled in the middle and had a 9” quilt block?  Each would be 3”. 

Center Square

That center square is the easiest of the three to figure the cutting size.  It’s the finished size plus ½”. 

Striped Squares

The four striped squares are similar to the Rail Fence blocks from the earlier example. 

The height of these squares is the same as the height of the block plus ½”. The width is half of the width of the block plus ½”.

Too much math?  Remember our 6”, 9” and 12” block examples above?

To make a 6” finished Churn Dash block, this piece will be made of a light pink rectangle that measures 1½” wide by 2½” tall and a background rectangle the same size.

For a 9” block, the measurements will be 2” wide by 3½” tall.

The 12” block will use pieces that measure 2½” by 4½”.

Triangles

The corner units for these Churn Dash blocks are Half Square Triangles.  And for these little guys, the math is already done! 

Pop on over to this Half Square Triangle Tutorial for all the details on how to adjust the size of this part of the Churn Dash block.

This is what it might look like to make a Churn Dash quilt. You better believe I put these blocks that I’ve never made before onto my To Quilt List!

Baby Blitz Quilt

All of the directions to this point have been theoretical, how to adjust a quilt block size for any block you might encounter.  Go forth and quilt!

Or, read on for the specific adjustments I made to the Blitz Quilt Block to make this baby quilt.

This baby Blitz Quilt is made of two different blocks. It follows the pattern directions in all aspects except for the cut size of the blocks.

The triangle blocks are half the height and half the width of the regular Blitz blocks.

For the square blocks, rather than resize the cutting dimensions, I made my blocks 2 squares by 2 squares, instead of the original 4 squares by 4 squares.  That way, they are also half the height and half the width but I didn’t have to sew together itty bitty pieces.

Now that you know how to adjust a quilt block size, here are a few more Blitz quilts. Like I said above, I have yet to find a color a combo that doesn’t work for this pattern.