|I can never remember hem depths so I keep a chart handy.
Ultimately, hem depth is determined by your fabric's unique characteristics. I often look at high end garment depths to determine what is best. They don't skimp on hems so that the garment hangs properly. You don't see a hem curling up unless that is the intention.
Here is some info from Threads magazine that I use as a starting point and have found that it is good as a general guideline.
"As a general rule, the straighter the skirt/pant/sleeve, the deeper the hem. The reason is that a deep hem depth -also called the hem allowance-is tricky to ease up into a flared garment."
Basic Straight skirt - 2-2 1/2 inches
A line skirt or tailored trousers - 1 1/2 -2 inches
Full gathered skirt 1/2- 1 1/2 inches
circular, curved or bias cut skirt 3/8-5/8 inch
Information from Threads Article "end on a good hem".
when marking your hem line, do not mark where you are going to fold the fabric but instead mark the line where you are going to fold to.
So if you have a 1 inch hem, mark at the 2 inch point and fold fabric up until the edge of the fabrics hits the mark.
Why this idea took me decades to figure out, I'll never know.