Reading dimensions without guessing
Product photos can be useful for appearance. Written measurements are the place to start when comparing size.
Identify what is being measured
A listing may describe overall length, usable length, width, diameter, or circumference. These terms are not interchangeable. Look for a labeled diagram and confirm the unit. If a measurement is missing, ask the retailer; do not infer it from a hand, a prop, or the scale of a photograph.
Compare like with like
Put measurements into the same unit before comparing two products. Keep overall and usable dimensions in separate columns. The converter on this site changes inches to centimeters; it does not identify a suitable size for your body. A mathematically correct conversion cannot answer a personal comfort question.
Keep comfort outside the competition
There is no reason to treat a larger size as an achievement. Consider the kind of product, its intended use, and its instructions. Take uncertainty seriously and stop if something is uncomfortable. If you have pain or a health concern, get individual guidance from a qualified clinician rather than relying on a size chart.