Photo courtesy of, click photo to enlarge image

Length checking is a way to measure the length of your hair. Length checking is a way to track your hair journey, your progress in other words. The average hair growth is about six inches per year, some achieve more, some achieve slightly less than the average, but the way to track that is by length checking.

Keep in mind that length checking is just checking the growth that you have RETAINED, not the actual GROWTH accumulated between progress checks. 
Click to enlarge hair chart

Before I tell you how to do a proper length check, let's look at how each length looks at the levels of growth.

I'm not for sure what this length would be called but I'm going to just call it above ear length (AEL):

EAR LENGTH (EL): Hair touches the ear in this stage.

NECK LENGTH (NL): Hair is now past the EL stage and is touching the base of the neck. NL varies due to body composition. Some people have necks, some have short necks. Despite what people say, EVERYONE has a neck.
SHOULD LENGTH (SL): Hair has now fully passed the NL stage is touching the shoulders, this stage varies due to form of the body. Some people have high shoulders, some have low shoulders.

ARMPIT LENGTH (APL): Simply hair that touches the armpit.

BRA STRAP LENGTH (BSL): Some people don't like to use this as a length check because everyone wears their bra's different. Basically, it's when hair touches the top of the bra or reaches the bra strap.
This is me btw =D

Mid-Back Length (MBL): When hair passes the bra completely. 

Waist Length (WL): Self explanatory


Hip Length: 
 Personally, I prefer to do length checks using the body. The T-shirts that are out there are helpful but I just prefer see how the hair looks on my body.