Rules of thumb for Adult watch caps in K2, P2 ribbing
Using appropriate yarn, the following number of stitches on these size needles gives me the right circumference for an average head.
US Size 15 - 48 or 52 stitches
US Size 13 - 60 stitches
Metric 8 mm - 64 stitches
Metric 7 mm - 68 stitches
US Size 6 - 96 stitches
I actually use a P2, K2 ribbing, because of how I decrease for the crown.
I usually knit a P2, K2 ribbing tube for about 9 inches (depending on how long a cuff you like) and then do the following
First decrease round: P2tog, K2tog across round (You've made a
P2,K2 ribbing into a P1,K1 and decreased by half)
Second round: P1, K1
Third round: K2tog. Again, you've decreased by half across the
round.
Putting the purl stitches first makes the K2tog look smoother, as they
swallow up the purl stitches and leave only knit stitches.
Fourth round: K
Fifth round: K2tog.
Break yarn, thread through remaining stitches and pull tight.
It's an easily memorized method, and you can churn out hats with these formulae!