Hexagons & Triangles, easy way to calculate size?
 

So I took a class last weekend and learned how to make this:
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These are obviously only partially sewn together at this point; I have more blues I'm going to mix in so this was just the start I got during class where I only had 3 colors with me.

I'm trying to figure out if there's an easy way to figure out how many hexagons and how many triangles I need to make a king size quilt.

Each hexagon is 6" finished, measuring flat side to flat side. (Top to bottom, in the picture above). So I end up with rows that finish at 6", so height is easy.

Width, though...these aren't going to be 6" from point to point; it's going to be more. Can anybody tell me what that formula is?

I know I could just measure these and find out, but I want to know the math, so next time when I'm designing something like this I can figure it out before cutting & sewing anything together.

And then the triangles...I THINK I need 2 triangles per hexagon..? Does that look about right?

I think I can just sort of ignore the triangles in the measurements, since those just sort of fill in between the hexagons. Alternating rows end with half-hexagons on both sides, so it's always the same number of hexagons per row even though they're offset. But I still need to figure out how many triangles to cut.

I have a bunch of fabric cut, but I haven't counted anything yet.

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This is going to be a pretty quilt!

If my calculations are correct, a hexagon 6" side-to-side will be 6.93" point-to-point. The formula is:
(side-to-side) x 1.155 = (point-to-point)

Yes, you will need 2 triangles for every hexagon (plus or minus a handful, depending what you do at the edges).

If you want more explanation of my formula, I can do that; I just didn't want to clutter this up with triangles and the square root of 3 and whatnot if you don't want it.

Good luck!

Oh by all means, share! I was really good at math in high school but I've forgotten everything about geometry since then! I will probably remember it better if you go into more detail. (If you don't mind, of course; you've given me what I need already, and thank you for that!)

I'm on a huge aqua/turquoise and orange/tangerine kick lately. I used to HATE orange but now I'm becoming pretty fond of it! Fond enough that I want to make this our spring bed quilt. :)

Here is a link to how to calculate hexagon dimensions:

http://www.had2know.com/academics/he...alculator.html

When someone says they are doing a "one-inch hexagon" - I never know which dimension is being use -
side length, height, or "diameter"

What a great site that is!! For more than just hexies. Thanks!

the general "rule" is that hexagons are measured by their their side

the width at the widest point is twice the measurement of one side

when drafting a hexagon, you use the radius to draw a circle, then is THE SAME measurement to mark off six points around the circle

then draw straight lines between the points

hope that helps

Awesome! Thank you bearisgrey!

Our teacher talked about confusion in hex measurements; she told us that for normal piecing the size is usually height ("flat to flat"), for paper piecing the size is usually a side...but everybody breaks the rules and mixes things up. :shock:

Thanks for the triangle/hexi info and calculations.

Thanks for the "rule" about hexagons being measured by their side length.