Quilting Blog

How to Accurately Trim Large Quilt Blocks (With the Rulers You Already Own)

Big block quilts can be quick, easy and fun to stitch together, but how do you properly trim the individual blocks if the tools you have on hand are not large enough?

pinwheel block

It's not difficult at all!  Using a 6" square ruler, this large pinwheel block will be trimmed into a 10" square. Just another great quilting hack to add to your quilting knowledge!

pinwheel quilt block

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How to trim squares for big block quilts

Step 1: 

Determine the desired "trimmed" block size and divide that number in half.

In our example below, the pinwheel will be trimmed into a 10" block.  Therefore, 10" divided in half equals 5". (Remember to add seam allowance to your trimmed block size)

Step 2:

Place the 5" ruler marking directly on the horizontal and vertical center seams, and align the 45 degree line of the ruler on top of the 45 degree seam of the block.

If you do not have center or diagonal seams lines, fold your block to determine the center and press in centered horizontal, vertical and diagonal lines.  Use these as your guide.

pinwheel quilt blockpinwheel quilt block

Step 3:

Once the horizontal and diagonal lines are in position, hold the ruler in place.  Without shifting, trim away as much as the ruler will allow.

pinwheel quilt block

Step 4:

Rotate the block one time. Re-position the ruler, aligning the center seams and the 45 degree seam exactly as in the previous step. Continue to trim the right side of the block and across the top as far as the ruler will allow.

pinwheel quilt blockperfect corner seam

You should rotate and trim the block total of four times.  

pinwheel quilt block

There you have it — a 10" block trimmed with a 6" ruler.

Do you have another strategy for trimming large blocks? Leave a comment sharing your method for trimming large quilt blocks. We'd love to know!

Anxious to get started on a big block quilt of your own?

great big block quilt

Photo via laugh yourself into Stitches* Craftsy pattern store

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22 Comments

Janet Espeleta

This is a great hint. However, you should have said to put your ruler on the 5-1/4″ mark for a block that will finish 10″. Otherwise, you end up cutting off your seam allowances.

Reply
karen walker

Thank you Janet

My 10″ block example represents an ‘unfinished’ block size. It is easier to photograph in whole inch increments. You are correct in your comment, if one wants a 10″ finished block, they would use the
5-1/4 mark on the center seam. Thank you for clarifying, I appreciate it! 🙂 ~karen

Reply
Chrissy

Yes!

Reply
Joann

What a ridiculously simple idea and it never even occurred to me.
I have some 19 and 1/2 inch blocks to square up and this will
make it quite simple. Thank you.

Reply
Anne

What a great tip! I never thought of doing it this way, but I will remember this!! Thanks.

Reply
Toni

You should have said something at end of your presentation about seam allowance because alot of people don’t read comments. I aleays do, you pick up great tips from their comments. Thank you.

Reply
Charleen

Yep, she did me tion seam allowances toward the beginning. I almost missed it.

Reply
Marcy Williams

Great tip. There’s also a wonderful 20″ square ruler out there. Love mine for this, squaring up quilts for binding, and lots of other uses!

Reply
karen walker

Thanks Marcy! I should probably invest in a 20″ square ruler! 🙂 Especially when it comes to squaring up for the binding!
Thanks for your comment.
~karen

Reply
Jean Scofield

I waited for the best sale price and the best coupon I can use to treat myself and buy the 20″ from JoAnns. In the end I got it for 25% of the retail cost. Since JoAnns changed their dates and amounts for coupons recently you really have to watch for the “window” to get both discounts. These days I wait for their “X %” off your entire purchase good for regular and sale prices for your entire order. Fortunately they are offering the total price coupons more frequently.

Reply
Julie

Ok, it must be me, but i’m really confused by the pictures of your ruler on the square. Your origin may be on “center” of the fabric, but the lines of the ruler are way off the seams (both vertical and horizontal) once you get away from the origin. Is all you care about that the 45 degree line lies on the 45 degree seam?

Additionally, I’ve read in several of the blogs here about where the ruler should lay when cutting fabric and where the ruler lines should lay. (for example, when cutting a 2″ strip from a bulk piece of fabric, the ruler lays on the 2″ piece, and the entire 2″ ruler mark should lay on the fabric of that 2″ piece to be cut.) However trimming blocks is a different example and I thought this blog would answer my question but I think it’s too difficult to see on the photos. Can you tell me the answer to this question. I have a block i need to trim down to size. The perimeter of the finished size has a stitch the whole way around it. I need to make a half inch seam allowance from that stitch. When I lay my ruler on the block and attempt to line up the 1/2″ mark on the ruler to the seam, how exactly should that fat ruler mark lay in regards to that seam (I’m right-handed). Should the right edge of the mark (i.e. the inside edge of the mark) lay on the right edge of the seam? Should the right edge of the mark lay on the center of the seam, or the left edge of the seam? It may seem like a silly question, but from everything I’ve learned about quilting, even the width of a single thread is important when it comes to sewing things together.

Thank you for your time!
Julie

Reply
karen walker

Hi Julie,
Thanks for sharing your thoughts…
The intent of my post is to show how to square up a large block using a ruler smaller than the desired block size.
In your comment, you say…
“Your origin may be on “center” of the fabric, but the lines of the ruler are way off the seams (both vertical and horizontal)”
If you are referring to my photo…looking very carefully at the picture, my horizontal and vertical lines may not be ‘exactly’ lined up on the corresponding seam lines. They may be an 1/8″ off. My block may not be exactly perfect. 🙂 But…the 45 degree line is key as well as maintaining the horizontal and vertical lines as close to perfect as possible.

Without seeing pictures of your block, it’s hard for me to fully grasp your situation. With that said, and if i am understanding correctly, i would place the line of the ruler on the seam (or do you mean the stitched) line. Sounds like you may have 4 areas on your block (with the addition of your stitched line) that will help you square up your block. The vertical seam line, the horizontal seam line, the diagonal seam line and your stitched line that encompasses your block.

If you’d like more clarification, you are welcome to email me and send a photo.
chezstitches@gmail.com

Here’s my post on proper rotary cutting. It is really important to lay the ruler line on the fabric! 🙂
http://www.craftsy.com/blog/2014/02/how-to-cut-fabric-for-quilting/

Thanks Julie!

Reply
anna ramos

some thing new learned.

Reply
Linda

This tip was extremely helpful. I have a gazillion rulers but I never seem to have the right one for the project at hand.
Sincerely appreciate the info.

Reply
Bess C. S.

Thanks so much! I’ve been on a long search for info on big block trimming. This is so helpful!

Reply
Julia

Wish I had seen this post 2 weeks ago when I had a bunch of large blocks to square. Great info. Thanks a lot.

Reply
Glenice Jones

I agree with some of the comments here – information on trimming large blocks is very hard to find. I need to trim my appliqué blocks to 24.5″ and could not find any information….. so I went to a local plastics store and bought a 24.5″ piece of Perspex with etched diagonal and cross lines to help centre the block.
Karen, to use your very helpful tutorial, I would need to use at least a 12″ square – correct?

Reply
karen walker

HI Glenice,
you would need a 12-1/2″ square ruler. You’d place the 12-1/4″ (which is half of your 24-1/2″ block size) in the center of the block. If you don’t have seams to follow, like in the pinwheel pictures, you could lightly press your block horizontally, and vertically to identify the center…as well as diagonally. Or, you could mark the block. I think you idea of the etched Perspex for such a large block is a great idea. Thanks for sharing.
~karen

Reply
Sandra W.

For those making large blocks, I’d say the Creative Grids 20 1/2″ square ruler will eliminate this as a challenge. It’s a one-time cost to eliminate this frustration.

Reply
karen walker

I agree…a 20-1/2″ square ruler would be a great investment. However, if you’re stuck like i was…this is a great alternative.
Thank you Sandra 🙂
~karen

Reply
Jean Scofield

I have used two rulers side-by-side to square up and trim large blocks. Put the rulers next to each other and line up the measuring lines. If adding the second ruler gives the extra inches you need use them together as one ruler. Divide your block size by two (half the width) and measure from the center seam to the edge and trim (don’t forget to add the seam allowance). Turn the block so you can trim the opposite side. Make sure the ruler doesn’t shift off the center seam when you turn. Finally you trim the top and bottom the same way. You corners should come to a point just as Karen describes.

If your two rulers are long and wide enough to create a square larger than the whole block you can use them together side-by-side to trim the whole block. Again treat them as if they are one ruler. Hope this is clear and helps. Jean

Reply

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