Before purchasing car film, it is important to measure the dimensions of your car windows. Here's how to do it:

Height of the glass:

1. Locate the top edge of the window glass, which is usually hidden inside the door frame when the window is rolled up. Roll the window down a bit to see it.
2. Using a tape measure, measure from the top edge of the visible glass to the bottom edge where it meets the door panel. This is the height of the glass.

Total length of all windows:

1. Measure the length of each window from left to right (or vice versa) along the bottom edge. Include the rear window, the windshield, and any small quarter windows.
2. Add up all these measurements. This total is the length of all windows.

Remember, it's always better to overestimate than underestimate. It's recommended to buy a bit more film than your measurements suggest to account for mistakes and wastage during installation, especially if you're doing it yourself.

Also, consider the complexity of your windows. Curved or complex-shaped windows may require more film. Lastly, please be aware that some states have legal restrictions on the darkness of window tinting, so be sure to check your local regulations before proceeding.