Calculating Borders to Fix Size Problems

Yesterday I showed you my Flip Side quilt using triangles I’d cut for play. When I made those triangles, I cut 5″ squares, which make finished half-square triangles of 4 1/8″. Why did I cut them that size? Because I was just playing with color and shape and had no plan for using them.

When I did use them in a border, I had an odd size. The finished border width was 4 1/8″. To attach them as whole blocks (not whacked off in a “liberated” way), the prior border and next border needed to work with some multiple of that length, too. With 7 blocks along a side, not including corners, the length is 28 7/8″. With corners, there are 9 blocks measuring 37 1/8″.

Numbers like these are not easy to work with if you want to use pieced borders adjacent to them. Some of you may be thinking this was easy to solve, and indeed it was. I could have trimmed my HST to finish at 4″. Then I would have had border lengths of 28″ (for prior border) and 36″ after attaching the triangles. But I didn’t.

So given that I have weird sizes, how should I deal with that? First, let’s draw a picture…

Flip Side mockup

This is an idea of what I was working with. Assume the center block is 14.5″ (another weird size!) and the orange border takes the center to 20.5″. To add the 7 HST blocks evenly on a side (not including corners,) the center needs to be 28 7/8″ long after adding the bronzey middle border.

Adding a spacer border
In essence, the bronze border is a wide spacer border. Some people call this a framing border or coping border. How wide does it need to be? To find the finished width

X = length of actual border already attached to center
Y = length you want the spacer border (length of the new border to attach next)
Z = (Y – X) = total adjustment
Z/2 = (total adjustment)/2, or width of spacer border

Example:
28.875″ – 20.5″ = 8.375″ or 8 3/8″
8.375″/2 = 4.1875″ or 4 3/16″. Note this is positive. I will ADD 8.375″ in total. Assuming each side is the same width, the bronze border will finish at 4 3/16″. (Note, they don’t have to be the same width. That would be typical but it is a design decision. Remember in total they need to finish at 8 3/8″.)

Let me do another example with easier numbers. Let’s say on a different quilt I want to use 5 6″ shooflies as my next border. That’s a 30″ long border. And my prior border takes my center to 28″ finished. I will need a spacer border to make the shooflies fit.

30″ – 28″ = 2″
2″/2 = 1″. The spacer border will need to be 1″ wide, finished measure.

Trimming the prior border
Let’s go back to the Flip Side quilt. What if I’d already attached the bronze border and it was 5″ wide, finished? At that width, the total center (center block, orange border, and bronze border) would be 20.5″ + 5″ + 5″ long, or 30.5″. It is too long to be able to attach the HST border.

The bronze border is unpieced strips, so my easiest option is to trim it to make the center smaller.

Here is the math:

X = length of actual border already attached to center
Y = length you want the border (length of the new border to attach next)
Z = (Y – X) = total adjustment
Z/2 = (total adjustment)/2, or width to trim off each side

Example:
28.875″ – 30.5″ = -1.625″ or -1 5/8″
-1.625″/2 = -.8125″ or -13/16″. Note this is negative, meaning I have to take away. Assuming each side is the same width, I’ll trim 13/16″ from each side, or slightly less than 7/8″. (Note, they don’t have to be the same width. That would be typical but it is a design decision. Remember in total I’d need to trim 1 5/8″.)

Summary
You can see the math is the same whether adding a spacer border or trimming from the center. You might use this method to adjust for piecing accuracy issues, or if you use a border stripe that has an odd dimension, or just to get from one border to another. If you participate in round robins, you know other group members can leave things awkward for your next step. In medallion quilts, spacers often are appropriate just to give a breather between pieced elements, or to add definition to an edge. In block quilts you might need a spacer between the center portion of the quilt and a pieced border.

It’s one more tool for your box that gives you more flexibility in your designs.

 

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12 thoughts on “Calculating Borders to Fix Size Problems

  1. KerryCan

    Oh my! I pride myself on my skill with measuring and fractions but, honestly, what you just wrote might make me avoid medallion quilts altogether! Still, the sense of accomplishment must be amazing.

    Reply
    1. Melanie McNeil Post author

      I don’t actually need to deal with this a lot, so I wouldn’t let that stop you! But when you need to add or trim, it helps to know how much. Thanks for taking a look.

      Reply
  2. snarkyquilter

    I’m impressed you make those odd fractions come out all right. I’m of the round up or round down school to make things fit. And yes, one advantage of wonky, improvisational piecing is more flexibility in fitting bits together with coping strips. A cop out? Absolutely.

    Reply
    1. Melanie McNeil Post author

      In truth, while I’ll do the calculations, I am not that precise in what I actually attach or trim. Fabric has a wonderful plastic nature and can stretch or scrunch that other 1/8″ (and beyond) pretty easily. I really showed this as a real-life example, whereas most of the time I don’t deal with numbers like these.

      As to coping strips, I am a big fan!

      Reply
  3. cjh

    I’m happy that you can think through (and enjoy doing so) and solve the math in quilts, because sometimes that is just the help I need, that I don’t want to think through!

    Reply
    1. Melanie McNeil Post author

      🙂 Thank you! Yes, I do a lot of borders, all different sizes. I tend to use a pretty small number of blocks in them, however, so am always looking for inspiration. Easy blocks used different ways… that’s the key, I think. Your 9-patches are just so fun. I’m looking forward to figuring out how to use them.

      Reply
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