I have received a few questions about how I size the chemo hats,
so I thought I would write it out here.
I have accumulated notes from all over the web, none of these ideas are
unique to me! But hopefully having them
all consolidated in one area will help. **SKIP TO THE BOLDED AREA IF YOU ARE JUST WANTING THE NUMBERS. **

There is no way to say "make x rounds" to get the right sized hat. There is so much variance, with stitch height, hook used, yarn used, and the actual gauge that one crochets - there are no hard and fast numbers. So I measure across the hat, in inches. This makes it consistent, regardless of the variables listed above.

Hats are generally made in 2 sections. First are the increasing rounds at the crown
of the hat. Second are the rounds of the
hat that fill out the body, or the height, of the hat. I use the guidelines on

Bev’s Country Cottage site for the measurements.

Women’s head circumference: 20”-22” and a hat height of 11”

Men’s head circumference: 22”-24” and a hat height of 11”-11.5”

I try to make a variety of sizes, in the ranges listed
above. When in doubt, I lean towards the
smaller sizes to help account for the missing hair of the average chemo
patient.

I start my hat
with increasing rounds, and continue until it measures the correct diameter as
below. (Circumference divided by 3.14
(pi) equals the diameter is the actual math used, but I just follow the numbers
below.) Regardless of the stitch used, it should measure to the diameter listed
below.

**To measure the diameter, I take my tape measure and stretch it from edge
to edge of the increased circle, across the middle. **

**SO, HERE ARE THE MEASUREMENTS I USE FOR HATS: **

**20” circumference hat needs a diameter of approximately 6.25”
across** (20/3.14 = 6.37”)

**21” circumference hat needs a diameter of approximately 6.5”
across** (21/3.14 = 6.69”)

**22” circumference hat needs a diameter of approximately 6.75”
across** (22/3.14 = 7.00”)

**23” circumference hat needs a diameter of approximately 7.25”
across** (23/3.14 = 7.32”)

**24” circumference hat needs a diameter of approximately 7.50” across** (24/3.14 = 7.64”)

Once I have the correctly sized circle for the crown of the
hat, I start working on the body of the hat. In most common patterns, this
means just to **continue rounds, without increasing, until the desired length of hat is reached, usually 11”-11.5”**. Don’t forget to take in account any border or
finishing edges you want to put in the hat – this needs to be counted in the
length as well.

(This is about as clear as mud. I am sorry.
Just measure your hat from edge to edge to figure out when to stop
increasing, using the numbers above and you should have the correctly sized
hat. If in doubt, lean towards the
smaller size, since hats generally have a good amount of stretch to them.)

Please let me know how this works for you!!