If you are talking about tub faucet -- if the tub is 15 in. high then about 28 in. to center of faucet -- if shower then about 48 in. from floor to center of faucet.
The height of a tub faucet should be about 40 inches, give or take a couple of inches, depending upon the height of each member of the family. The spout should be placed 4 inches over the top edge of the tub.
I usually fit them about 6" above the tub.
If not directly on the tub rim, mount it 6" above top edge of tub.
Another poster indicated 14 inches as the standard.
Standard height for ADA (handicap) is 42 " center of valve to shower floor.
A tub faucet acts as a shower and can be used to bath in the bath tub. It is a pressure valve which makes the flow of water through it constant and gives a nice shower.
height of a mop sink faucet