I made a king & cut 2-1/2" logs,,, finished 2",,, with the quilt so big I felt smaller logs woould. Be out of proportion.

I think the size will depend on how many logs you want in each block and how many blocks you want to make.

Working from size down....
Let's assume your king size is approx 100x100. 10 inch blocks would mean 100 blocks (10 x 10), but then you have to account for seam allowance, so you will end up 97.5 x 97.5.

If your block is 10" square, a center block plus 3 sets of logs would mean 10"/7, not a pretty number.

Let's start again. Working from block up....

let's say we want 3 sets of logs in each block. We want each finished log to be 1.5" x 7 = 10.5" + .5" outside seam = 11" finished (but 10.5 when blocks are pieced together). So each log needs to be 2".

Just examples of how to work it.
If you want help figuring out what size your logs need ot be given other variables, just PM me. I love the math part of this.

Eleanor Burns' Log Cabin Quilt in a Day uses 2.5" strips, making a 14" finished block. Works up great!

How much yardage of each color do you have? Log cabins have a lot of seams, so when you decide on a log & block size, do some calculations to make sure you have enough fabric. Seems to take more than you think ;-)

Quilt in a Day Log Cabin book has super fast rotary cutting techniques and wonderful ideas for lay out. I think they are about 12 1/2 inches.

Here is a schematic of the quilt I did, finished 14" blocks, quilt measured 126" x 140", but the client wanted it oversized.

kclausing: I will pm you any time I need math help.. I am an account and can't figure out quilt math for anything!

I find that it depends on how quick or the effect I want. I've made 2.5" strips for a "I want this to be quick" and I've done 1.25" to get to a blended effect. My avatar was 1.5" but wish I had done it 1.25" to get a better blending.