Ok, On a car, 32% is as low as you can go. That is 35% film with a 3% assumed tint from the factory.

You can always go darker but there is no reason to. I have 35% all the way around, including my windshield and no one can see in.

ONLY TRUCKS AND SUV's WITH MORE THAN TWO DOORS CAN LEGALLY PUT BELOW 35% AND THAT ON THE BACK WINDOWS!!!