How to Read Product Measurements

The four numbers

Total length is the whole product including handle or base. Insertable length is the portion designed for internal use. Diameter is the width at the widest point, and circumference is the distance around that point. Manufacturers usually publish the first three; circumference is roughly diameter multiplied by 3.14.

For internal products, insertable length and widest diameter describe fit. For external products, overall size describes how it sits in the hand. For rings, internal diameter and stretch describe fit.

Compare to something real

Numbers on a screen are abstract. Measure something familiar with a ruler and compare. Diameter in particular is easy to underestimate: a few millimetres is a noticeable difference in this category. When in doubt, choose the smaller of two options for a first product.

Units, listings and honesty

Listings mix inches and centimetres, and sometimes publish total length where a buyer expects insertable length. Read the specification table rather than the headline. If dimensions are missing altogether, that is a reason to choose a different product.

This book does not reproduce or freeze listing dimensions. The product page is the authority at the moment of purchase.