The darkest window tint percentage is 5 percent. Many limousine windows are tinted to this percentage of darkness, and it is impossible to see through it from the outside.
Visible Light Transmission Percentage, or VLT, is the term used to describe the darkness of the window tint. Higher numbers indicate lighter tint, with 50 percent VLT indicating almost no tint at all.
States have laws about the percentage of window tint allowed on vehicles, with the degree varying by state. It is a good idea to confirm how much tint is legal before applying it to a vehicle.