Sizing Formula for Crochet Hats

Recently over the holidays I ran into a fellow crocheter who had some awesome knowledge to share. I for one LOVE math which is why I think crochet designing is so much fun for me. However I was INTRIGUED when she told me that there is a math formula to figure out hat sizes. Seeing how this is something that I am really interested in and was finding it difficult to determine sizes, I started taking notes.

After I got home I started crunching numbers and comparing the results with other sizing charts and I was floored that the formulas were pretty accurate. I will for sure be keeping this in mind for the rest of my crocheting life. HAHA.

So this is how she broke it down for me.

Crochet Circle

Formulas for finding crochet hat sizes. 

Circumference (divided by) 3.14 = Size of Crochet Circle

Circumference (divided by) 10 = ? (multiplied by) 4 = Hat Height

Circumference (divided by) 2 = Hat width

*** These formulas will work with Most hat patterns but not all depending on the pattern type***

  

 For example......

0-3 month old - Circumference = 12 - 14 inches

Circle Size

 12 / 3.14 = 3.8 (round nearest whole number or .5)  

14/ 3.14 = 4.4 (round nearest whole number or .5)

so your circle size would be 4 inches to 4.5 inches

Hat Height

12 / 10 = 1.2 * 4 = 4.8 (round nearest whole number or .5)

14 / 10 = 1.4 * 4 = 5.6 (round nearest whole number or .5)

So your hat height would be 5 inches to 5.5 inches

Hat Width

12 / 2 = 6

14 / 2 = 7

So your hat width would be 6 inches to 7 inches

Neat huh?!?!?!?!

For those that don't enjoy math like I do I have it all broken down for you below. I hope you enjoy!!!!

Newborn - Circumference = 12 inches

Circle Size

 12 / 3.14 = 3.8 (round to the nearest whole number, .75, .50 or .25)

so your circle size would be 4 inches to 

Hat Height

12 / 10 = 1.2 * 4 = 4.8 (round nearest whole number, .75, .50 or .25)

So your hat height would be 5 inches 

Hat Width

12 / 2 = 6

So your hat width would be 6 inches to 

0-3 month old - Circumference = 12 - 14 inches

Circle Size

 12 / 3.14 = 3.8 (round nearest whole number, .75, .50 or .25)

14/ 3.14 = 4.4 (round nearest whole number, .75, .50 or .25)

so your circle size would be 4 inches to 4.5 inches

Hat Height

12 / 10 = 1.2 * 4 = 4.8 (round nearest whole number, .75, .50 or .25)

14 / 10 = 1.4 * 4 = 5.6 (round nearest whole number, .75, .50 or .25)

So your hat height would be 5 inches to 5.5 inches

Hat Width

12 / 2 = 6

14 / 2 = 7

So your hat width would be 6 inches to 7 inches

3-6 month old - Circumference = 14 - 16 inches

Circle Size

14/ 3.14 = 4.4 (round nearest whole number, .75, .50 or .25)

16/ 3.14 = 5.0 (round nearest whole number, .75, .50 or .25)

so your circle size would be 4.5 inches to 5 inches 

Hat Height

14 / 10 = 1.4 * 4 = 5.6 (round nearest whole number, .75, .50 or .25)

16 / 10 = 1.6 * 4 = 6.4 (round nearest whole number, .75, .50 or .25)

So your hat height would be 5.5 inches to 6.5 inches

Hat Width

14 / 2 = 7

16 / 2 = 8

So your hat width would be 7 inches to  8 inches

6-12 month old - Circumference =  16 - 18 inches

Circle Size

16/ 3.14 = 5.0 (round nearest whole number, .75, .50 or .25)

18/ 3.14 = 5.7 (round nearest whole number, .75, .50 or .25)

so your circle size would be 5 inches to 6 inches

Hat Height

16 / 10 = 1.6 * 4 = 6.4 (round nearest whole number, .75, .50 or .25)

18 / 10 = 1.8 * 4 = 7.2 (round nearest whole number, .75, .50 or .25)

So your hat height would be 6.5 inches to 7.25 inches

Hat Width

16 / 2 = 8

18 / 2 = 9

So your hat width would be 8 inches to 9 inches

1-3 year old - Circumference = 18 - 20 inches

Circle Size

18/ 3.14 = 5.7 (round nearest whole number, .75, .50 or .25)

20/ 3.14 = 6.36 (round nearest whole number, .75, .50 or .25)

so your circle size would be   6 inches to 6.5 inches

Hat Height

18 / 10 = 1.8 * 4 = 7.2 (round nearest whole number, .75, .50 or .25)

20 / 10 = 2.0 * 4 = 8.0 (round nearest whole number, .75, .50 or .25)

So your hat height would be 7.25 inches to 8 inches

Hat Width

18 / 2 = 9

20 / 2 = 10

So your hat width would be 9 inches  to 10 inches

3-10 year old - Circumference =  20 - 22 inches

Circle Size

20 / 3.14 = 6.3 (round nearest whole number, .75, .50 or .25)

22 / 3.14 = 7.0 (round nearest whole number, .75, .50 or .25)

so your circle size would be 6.5 inches to 7 inches 

Hat Height

20 / 10 = 2.0 * 4 = 8.0 (round nearest whole number, .75, .50 or .25)

22 / 10 = 2.2 * 4 = 8.8 (round nearest whole number, .75, .50 or .25)

So your hat height would be 8 inches  to 9 inches

Hat Width

20 / 2 = 10

22 / 2 = 11

So your hat width would be 10 inches to 11 inches

Teen to Adult - Circumference =   22 - 24  inches

Circle Size

22 / 3.14 = 7.0 (round nearest whole number, .75, .50 or .25)

24 / 3.14 = 7.6 (round nearest whole number, .75, .50 or .25)

so your circle size would be 7 inches  to  7.75 inches

Hat Height

22 / 10 = 1.8 * 4 = 8.8 (round nearest whole number, .75, .50 or .25)

24 / 10 = 2.4 * 4 = 9.6 (round nearest whole number, .75, .50 or .25)

So your hat height would be 9 inches to 9.5 inches

Hat Width

22 / 2 = 11

24 / 2 = 12

So your hat width would be 11 inches to 12 inches

I hope that all makes sense and I hope this helps with sizing your hats in the future!!!

In the mean time Here is a hat I made for my oldest son recently to match his new winter jacket. The pattern is the Griffin Hat by Sincerely Pam

I look forward to finding more tips and tricks to share with you this next year along with a few other fun things. Until then...................

Happy Crafting