Hi Holly,
There are so many ways to answer this seemingly simple question, but TLDR I would estimate that one average scale would measure less than 1 gram!
Scales on a snake are similar to your finger nails in that they help protect your skin, and come in different shapes and sizes even on your own hands! Since scales run down the entire length of a snake, their shape and size will change from one end to the other, with the larger scales being in the middle of the snake's body. Just like our finger nails, the size, shape, and color of the scales will differ between snakes, even if they're the same species!