Measuring for a wig

Step 1:  Measure the circumference.   Petite 21-21.5 in,   Avg 22-22.5in and  Large 23-23.5in 

Step 2:  Measure from hairline to hairline.   Petite 11-11.5 in,  Avg 12-12.5 in, Large 13-13.5 in 

Step 3:  Measure from ear to ear with a fingers width above ear. Petite 10-10.5 in, Avg 11-11.5 in, Large 12-12.5 in. 

If you run between two sizes, say you are measuring as an average in circumference and ear to ear but run large from hairline to hairline a large would probably be your better fit in our experience.