There are numerous site or blogs on the internet that summarizes the prescribed allowable tint shade levels and other restrictions for each state. But a general rule of thumb suggests that the front windshield and windows to be the most restrictive. However, each state has its own tint laws which are oftentimes not aligned with other states. For instance, New Mexico allows as low as 20% tint shade levels while Pennsylvania only allows up to 70%. Other states does not even allow window tinting altogether. Since most states are not on the same page, it is advisable to be familiar with the allowable tint shade levels in your state to avoid transgressions.