The RAM is about 256 MB. The internal memory of the Kin OneM is 4GB, so about 3.7GB are available for phone memory. There is not an exact amount of messages, as message sizes vary. But if you are looking for a magic number try 8,000 messages. Theoretically it can hold more, but that is a good number to delete messages at. Keep in mind those numbers are for average size text message. This is assuming each message is 1KB.