What is Free shipping threshold?
A free shipping threshold is the minimum cart value at which shipping becomes free. Set it too low and shipping eats the margin; set it too high and shoppers abandon the cart.
A margin-safe starting point is the blended shipping cost you absorb divided by the part of your margin you are willing to give to shipping. The result moves with your margin, your zones and your product mix.
A threshold above your current AOV is the usual way to nudge shoppers to add an item.