Systems, devices, and methods related to on demand memory page size are described. A memory system may employ a protocol that supports on demand variable memory page sizes. A memory system may include one or more non-volatile memory devices that may each include a local memory controller configured to support variable memory page size operation. The memory system may include a system memory controller that interfaces between the non-volatile memory devices and a processor. The system memory controller may, for instance, use a protocol that facilitates on demand memory page size where a determination of a particular page size to use in an operation may be based on characteristics of memory commands and data involved in the memory command.