Formula to Determine How Many Stitches to Increase per Round in a Circle

When knitting or crocheting a circle and working from the center out, how many stitches do you increase to keep the work laying flat? Here is how:

Make a swatch at least 4” x 4” with the yarn and needles you plan to use for the project.

Measure the number of stitches and rows in 4 inches. Plug the counts into “a” and “b”:

a = 4/number of sts in 4 inches
b = 4/number of rows in 4 inches

Use this formula:

        pi(2b/a)       or      pi  x  2(b/a)

The answer is the number of stitches needed to be increased in every round!
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Let’s try an example:
Your swatch is worked in worsted weight yarn and in double crochet.

Your gauge swatch measures 12 dc and 7 rows in 4”

a = 4/12 = 1/3
b = 4/7 (multiply by two) = 8/7

3.14(8/7 ÷ 1/3) =

3.14(8/7 x 3/1) =

3.14(24/7) = 10.765

Increase 11 stitches per round.
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Another example is a knitted gauge of 20 sts and 28 rows per 4 inches.

a = 4/20 = 1/5
b = 4/28 = 1/7 (multiply by two) = 2/7

3.14(2/7 ÷ 1/5) =

3.14(2/7 x 5/1) = 4.48

Increase 5 stitches per round.

Of course, your pattern stitch will determine where to place the increases—you will have to balance out the increases to an average of 18 sts per round. One row may not have any increases and the next row may have double the increases--just make sure it averages out.