Have you ever wanted to make a crochet hat without a pattern, but didn't know when to stop increasing? Here's a helpful formula I learned from someone at CGOA (Crochet Guild of America).
First, measure around the person's head. Let's say their head measures 22" around.
Next, divide the circumference by 3.14.
Example: 22 / 3.14 = 7
That means that when your circle reaches 7", stop increasing and work even until you reach the desired depth.
Happy crocheting! :->