Here's a simple formula we use to find out how much material we need for rings given just the diameter. We usually ask clients who don't know their ring size to send us a photo of their existing ring placed on top of a ruler. We get the inner diameter in millimeters, add the thickness of the metal to be used in millimeters as well and multiply their sum by pi - approximately 3.14 - to get the circumference or length of material to cut!

In our intermediate classes, we can't count how many times we've been given death stares by students the first time we ask them to use pi. 😆 But in the end - as one of our students exclaimed after applying the basic formula - "Math is right!" 🙌