Measure the jar, look at the label sizes Thorne publishes, each label or series of labels has its size listed . I am currently using Thorne labels that are ± 64mm x 44mm on 227g (8oz) hexagonal jars. They look fine to me, they could have been larger or even smaller. To arrive at my chosen size I took my trusty tape measure to the shops and measured the size of similar jars and labels then decided what I liked the look of.