The most advantageous places for a bathroom grab bars are 36 to 38 inches above the bathtub floor. A vertical and horizontal grab bar should be placed on the control wall of the tub. This is where the shower head and the spigot are.
Ideally, these grab bars should be at least 24 inches long. Two horizontal grab bars should be installed on the side wall of the tub. These bars should be at least 24 inches long. The first bar should be 6 to 10 inches above the rim of the tub and the other 36 to 38 inches from the tub floor.
A grab bar at least 12 inches long should be installed on the back wall.