When it comes to measuring a penny's tread life, there are a few different ways that you can do it. One way is to simply look at the coin and see how much of the original design is still visible. If you can't see much of the original design, then the penny has probably been through a lot of wear and tear and its tread life is getting low. Another way to measure a penny's tread life is to use a special tool called a micrometer. This tool can help you get an accurate measurement of how thick the coin's surface is. If the surface is getting thinner, then that means the coin's tread life is also getting shorter.