The obtained number is the size of the hat. But for more accurate choice of a model the allowances should be taken into consideration.
Important: generally, a standard hat should tightly fit the head, that means, 0.5-1.5 (cm) allowance should be deducted from the originally taken measurements, for loose fit.
Other important hat parameters:
1. The bottom diameter: head circumference divided by 3.14 (the number pi), considering the deduction of 1.5-2 (cm) allowance.
2. The depth of a hat: measured from the top of the hat (the vertex) to the bottom line. The standard formula for calculating the depth: head circumference divided by 3.
- the depth for summer hats: head circumference divided by 3+1 (cm) allowance for loose fit;
- the depth for winter hat: head circumference divided by 3+2 (cm) allowance for loose fit.
Important: the standard depth and bottom diameter is considered for hats that cover the middle of the ear, for nonstandard hats the allowances for loose fit are different.
How the size depends on other parameters:
1. The hat pattern: if the hat has a volume pattern, when taking the measurement of the head circumference 1 (cm) allowance should be deducted from the result, considering the stretching.
2. Hat thickness: for a loose or volume hat, 1-2 (cm) should be deducted from the head circumference.
3. The fabric of a hat: cotton and wool shrink for 1-2 (cm) with time, acrylic and viscose, on the contrary, stretch for 1-2.5 (cm).
Important: for thick, non-stretching and smooth fabrics the allowances should not be considered.