Photo by CacheMania and used under the Creative Commons license.
There are FIVE basic sizes geocaches can be listed as:
1. Micro – A micro size geocache is only large enough to fit a small logbook and maybe a small pencil in the cache container. Typical containers of this size are 35 MM film canisters, plastic bottle preforms, bison tubes, Fisherman’s Friend boxes, pill bottles. Micros are the most common size of geocaches.
2. Small – A small size geocache is usually large enough to put in a logbook and pen or pencil and still have a small amount of space available for swag or trackables. Typical containers of this size are Tupperware style sandwich boxes. Beginning geocachers should start with trying to find size small or larger geocaches.
3. Regular – A regular size geocache is usually about the size of a regular loaf of white bread or an ammunitions box. Lots of swag and trackables can fit into a regular size geocache.
4. Large = A large size geocache is anything over the size of a five gallon bucket and there is no limit to how big they can actually be. Two of the largest I have found the propane box for and abandoned camper trailer and an equipment bin at an abandoned tennis court.
5. Other – Other is the catch all size for various caches like Earthcaches. A popular geocache container that fits into the Other category is the “NANO” container which is a little bit larger then a pencil eraser. Some cachers nano size caches as Micros but can really throw you off when you are looking for something quite a bit larger.
6. No Size Chosen – This is not really a size but it is possible to create a cache and not give it a size. A few examples of this is Event Caches, CITO Events, and Virtual Caches.