Children's sizes:  5 -12 years old: 53, 54, 55, 56
Kid's and women's sizes: 55, 56, 57, 58, 59
Men's sizes: 57 and up.

How to measure your head
Wrap a measuring tape around head, 1.5 cm (5/8 in.) above eyebrows and ears.
If you don't have a tape measure, use a string and then measure the string. Read the measurement in centimeters or inches,
add 1 cm or 0.4 inch to the measurement (only for winter hats),
and compare with the size chart.
If a result in between 2 sizes, go to the larger size.

Hat Size Conversion Chart

Russian 

Inches

US

53

20 7/8

6 5/8

54

21 1/4

6 3/4

55

21 5/8

6 7/8

56

22

7

57

22 1/2

7 1/8

58

22 7/8

7 1/4

59

23 1/4

7 3/8

60

23 5/8

7 1/2

61

24

7 5/8

62

24 3/8

7 3/4

63

24 3/4

7 7/8

64

25 1/4

8