There are a few methods to determine if your sunglasses are polarized.
The easiest method is to hold your sunglasses in front of a computer or phone screen. As you look through the lenses at the screen, rotate the sunglasses to a 90 degree angle. If the lens is polarized, when you look at the screen through the lens the screen will look strange – it may look slightly wavy, dark or even blank.
Another method is if you have two pairs of sunglasses: one pair being the pair you are testing and another pair you know are definitely polarized. Hold the confirmed polarized sunglasses behind the sunglasses you are testing. Turn the sunglasses you are testing to a 90 degree angle. If the combined lenses turn dark or nearly black, then your sunglasses are polarized.