# Quilt Blocks: Simple Math Part 3

We’ve been learning some basic quilt math and we’re up to Part 3. Are you still with me?!

If quilt math isn’t your strong point and you really want to wrap your head around these concepts, you might want to review Part 1 and Part 2.

What if you have a block diagram but no finished size and no patch dimensions? How do you determine how big you should make it, or how big you want to make it? This idea is similar to the ideas in Part 2, and yet different.

Let’s say you have the block photo above. Once again the first thing to determine is how many divisions there are across the block.

There are five, as you can see by the black lines I have drawn. Technically, you can make the block any size you want, but life will be simpler if you make the block so that each of the five sections is a nice round dimension, which will be rotary cuttable. Examples would be 1.5″, 2″, 2.5″, 3″ and so on. When you get up to about 4″, keep in mind that the block will be quite large, since 4″ x 5 sections is 20″. That’s a hefty block.

Let’s say you decide on 3″ per section for a 15″ finished block (that’s 3″ x 5 sections = 15″). Here are the patches you would need:

• 5 purple squares to finish at 3″ because they take up one section; add 1/2″ for seam allowance and you know to cut 5 squares 3.5″ x 3.5″

• 16 yellow squares to finish at 1.5″ because you can see they take up 1/2 of a section; half of a 3″ section is 1.5″; add 1/2″ for seam allowance and you know to cut 16 squares 2″ x 2″ (1.5″ plus .5″ is 2″)

• 16 purple squares 2″ x 2″ (same math as above)

• 4 each of green and yellow rectangles; you can see they are 1.5″ x 3″ finished so you add the 1/2″ seam allowance to both width and length and you get 2″ x 3.5″; cut 4 each of yellow and green rectangles 2″ x 3.5″

• Triangles: you can see they take up one section which is 3″. Add 7/8″ (we covered that in Part 2) and cut squares 3 7/8″ x 3 7/8″; cut 4 from yellow and 4 from pink/orange.

Look at the photo again: you see there are 8 yellow triangles and 8 pink/orange triangles. Why are we cutting only 4 of each? Because you’re going to cut them in half diagonally, which will result in 8 of each.

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This example of a 15″ block is pretty simple because the 5 divisions or sections divide equally into 15. You make life easier when you choose a block size that is divisible by the number of sections. In other words, this block would work well as a 5″, 10″, 15″ or 20″ block because those numbers are all divisible by 5, the number of sections in the block.

What if you really needed a 12″ block? Could you make this block finish at 12″? Absolutely you could, but the sections will not be an easily cuttable dimension because 12″ divided by 5 equals 2.4″—not so easily done with a quilting ruler. If you are determined to make the block finish at 12″, you’ll want to create templates. Quilt design software such as Electric Quilt’s EQ7 makes this a breeze. The templates would be funky dimensions, but with templates it doesn’t matter.

If templates send you screaming, another solution is to choose a different block that has a number of sections that divides neatly into 12, such as 2, 3, 4, or 6.

I think that’s enough quilt math for one day. We’ll dive more into the idea above in Part 4 next week.

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Put all that you’re learning into practice by checking out the Block Bonanza of 150 block diagrams in the March/April issue of Quiltmaker.

If you plowed through all this math and are still reading, you deserve a prize! Leave a comment by midnight Saturday, Feb. 23 and I’ll choose a winner for a little bundle of quilty goodness. Two winners! #3 and #14 have been notified by email. YAY!

I'm an editor for Quiltmaker magazine in Golden, Colorado, USA. For six years, I wrote pattern instructions, product reviews and how-to articles. Then I spent four years as QM's Interactive Editor, working to generate much of our online content. Now I'm back to patterns and how-tos, which is a great fit for me. I still love writing about quilt-related topics for Quilty Pleasures, and I always have my finger on the pulse of the quilting world. I teach a variety of quilt classes and give guild programs, too. Reach me by email: editor@quiltmaker.com.
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### 43 Responses to Quilt Blocks: Simple Math Part 3

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2. Verna says:

Part 3 was done on Feb 21 and promised “next week” for Part 4 but I have not seen it. Did I miss it??

3. Nancy says:

Wow! Thank you for the fabulous goodie box you sent me for this giveaway! I’m thrilled!

4. Miriam says:

Gracias por enseñarnos hacer los calculos para construir bloques. Es muy interesante y entretenido aprehender hacerlo por si mismo. Calcular bloques y con esas herramientas que nos brinda la posibilidad de crear otros nuevos.

5. N Codde says:

Quilt Blocks: Simple Math Parts 1 through 3 are very helpful. I’m looking forward to Part 4, when will it be available? Thank you! :^)

6. Diane Potts says:

This is invaluable information. I’ve only used prepared patterns and haven’t ventured out on my own. I can’t wait for the next installment. I have some fabric that I was going to use to make a “pattern” with, now I think I’ll try to make my own. Thank you.

7. Melody DeGraziano says:

I am mathematically challenged , to say the least, so I was leery about this exercise helping me. But I totally understood your break down on how to figure the size of block parts. You are indeed a fabulous teacher! Many thanks for giving me the courage to make blocks any reasonable size on my own.

8. Gina French says:

Thank you so much for this info. I would turn away from blocks that had many divisional cuts because it looked intimidating. Not anymore. What a great way to look at blocks. I am going to view them in a whole different light.

9. Nikki McDonald says:

It comes down to the old saying. “How do you eat an elephant?” Simple….
ONE BITE AT A TIME! You turned the light bulb on, in my mind….

Thanks

10. Cynthia Helms says:

Have always loved to figure out how to make a challenging block with no instructions. You have really helped with these tutorials!

11. Claudia says:

These little lessons take me back to my early quilting classes. So glad I took them. And if J Fontanella reads Quilty Pleasures, I hope you are still “in pieces”. I most certainly am.

12. CJ says:

I really do like math – but will have to re-read this!! Love the challenge!

13. carol l says:

So far pretty simple, looking forward to more math.
Carol L

14. Shasta says:

It really helps a great deal to be able to figure out how to make your own quilt by doing your own math, and to adapt patterns that you have. Thanks for the ideas, and for the drawing.

15. Cathryn H says:

I was just feeling comfortable after Part 2. Guess I’ll go back to the drawing board )

16. Doris B says:

Thank You so much ! I am printing these out to have them readily availabe by my cutting table. We all need a refresher course at one time or another.
Can’t wait for the rest of the weeks math.

17. Barb J says:

I’ve really enjoyed this series, and am looking forward to some more “quilty math”!

18. KT says:

Thanks for the great lessons. I’ve been figuring this out on my own, but it’s nice to have it so nicely laid out for us.

19. Lory Wood says:

Thank you, enjoyed the series!

20. Laura G says:

I’m going to have to read these posts a few times when I’m more awake. It looks like information I should use.

21. Donna Amos says:

Your tutorials are very good and the examples are easy to understand. I like doing the math of figuring how to change block sizes. Thanks for the giveaway.

22. sandygarrett80@gmail.com says:

I have always had fun figuring the math for certain blocks. Will definately get the mag for all the extra blocks. Thanks for the chance to win.

23. Cathy says:

Thanks for the invaluable information! I am a beginning quilter and find these math lessons extremely helpful. So helpful that I’m keeping them for future reference. Thank You for sharing your wisdom!

24. Linda Webster says:

Thanks for the tutorials! You’re taking the stress out of quilting math.

25. Nancy B from Many LA says:

These are some great lessons! Thanks! (And thanks for the giveaway!)

26. Jana Morgan says:

Thank you for the simple, practical explanations.

27. Not only am I still reading I’m chomping at the bit for the next lesson. I guess there is nothing new that I haven’t heard before but to have it all in one place is priceless! These lessons will be printed out and added to a special divider in my quilting ring binder!

28. Jnuquilter says:

I love this quilt math. I have often seen blocks I want to make but didn’t have the size to do so. Now I can take those blocks and make them with the knowledge you have given us. This is so awesome on how simple it is – thanks and keep this great information coming !!!

29. Barbara Murphey says:

You make it so simple. Now I say to myself “DUH, you couldn’t figure this out?”

30. nikki Mitchell says:

A lot if a ha moments!!!!

31. donna says:

The math makes alot of sense. Many thanks.

32. Lisa Marie says:

I guess math is one of those things you either love or hate. I happen to love it. Thanks for the refresher.

33. Okay, this series really IS interesting, but you should know that I almost didn’t read it when I saw the word “math” in the title!

I bought a wonderful Japanese patchwork book recently with beautiful photos of unusual blocks and block diagrams, but all the writing is in Japanese and there are no dimensions on the block diagrams. This series will help me figure out how to make some of them!

34. E. Engman says:

What if you used the metric system? On my ruler it looks like 30 cm is just c. 1/8″ less than 12″, so 6 cm pieces with seam allowances might work for a 12″ block.

35. Karlene says:

I love doing the math. You are doing such a great job with the tutorial and making it easy for those who struggle with it. It’s fun to follow along.

36. Carmen says:

Thanks for the great tutorial!

37. Leanne says:

Thanks for the quilt math…And we thought we’d never use math in the ‘real’ world! Thanks for the chance to win too.

38. LizaA says:

Great lessons! I’m saving for future reference. Thanks!

39. Becky Greene says:

These have been super-informative – I have pinned them for future reference. I love your illustrations about how think of the block in segments. Thanks for the giveaway chance, too – great bonus!

40. Nancy A says:

Thanks for the practical info and a fun giveaway.

41. Debbie M says:

That math was not too difficult! Thanks for the giveaway.

42. Annaleena Horning says:

Thanks for basic quilt block math lessons. These have been interesting. I have learnt a lot.