Crafty Threads 'n' Yarns

jacquie · Posted: Thu Jan 17, 2008 4:48 pm Post subject: Knitting a circle

The number of decreases/increases per row depends on the stitch/row ratio so may well be different for different thicknesses of yarn.

Here is how to work out decreases per row to make a circle from the outside to the middle- This would be useful if you were knitting a circular base to a bag that you had made from the top down.

you might want to get a calculator - pi is involved!

I am using 8 st/in and 10 rows/in and starting with 60 sts in this example - you'll need to plug your own values in.

1)Work out your circumference which is the starting number stitches / gauge

eg 60 stitches at 8 st/in gives 7.5 inches.

2) Next we have to work out the diameter (d) of a circle with that circumference (c) and c = pi x d
-> 7.5 = 3.142 x d
-> 7.5/3.142 = d = approx 2.38 inches

3) Now we need to work out the diameter one row into the circle which will be slightly smaller. We have 10 rows per in, and our biggest diameter was 2.38 inches. The diameter will get shorter by one row at each end so we need to subtract .1 x 2 from 2.38 which gives us 2.18 inches.

4) Nearly done! Next step is to work out the circumference of a circle with diameter 2.18 inches.
c= pi x d
-> c = 3.142 x 2.18 = 6.87inches (again slightly smaller, as we would expect)

5) Final step is to multiply up by the stitch gauge to get the number of stitches we'd want to have on the second row = 6.87 x 8 = approx 55 and then subtract this from the number first thought of (60) -> 60 -55 = 5.

5 is the magic number of decreases you will need to make on each row until you run out in the middle.

Miraculously this number stays the same for every row of your circle.

There is some approximating obviously as we need a whole number of stitches, but only round the final number you come up with in step 5 before subtracting from the number you first thought of and let your calculator deal with all the millions of decimal places.

_________________
Jacquie

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