How to Size a hat!

You just need to do some light math!

You will need a measuring tape.


Words to know:

  • Head Circumference= the distance around the head.
  • Diameter: the straight line passing from side to side through the center of a circle in this case the center of the crown portion

Things you need to know:

How to crochet in the round.

The trick to increasing in the round.

Formula to find hat diameter:

Head Circumference/ 3.14= Hat diameter

( / represents the division sign)


23in/3.14 =7.32in

13.5in/3.14 = 4.3in

Find the hat’s length from crown to ear using the head circumference.

Formula to find hat length:

Head circumference*4/10= hat length

( * represents the multiplication sign)



23in*4/10= 9.2in

13.5*4/10= 5.4in


Use the measuring tape to measure your circle to confirm you have the correct diameter.20160518_183519_Richtone(HDR)-1.jpg

Please let me know if this makes sense!!




6 thoughts on “How to Size a hat!

  1. Where do you measure the head to get the circumference? I see 2 possibilities: 1 – from the hair line at the forehead, down and around the ears to the hairline at the back of the neck; or, 2 – from the center of the forehead straight back to the back of the head just below the crown of the head. Also, do you have any recommendations for newborn and premie sizes. I have lots of partial skeins and I thought I would start making some small hats to donate to hospitals.

    Liked by 1 person

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