Editing WoW:Memory usage (section)

=== Tables ===
Unlike strings, tables can be altered, and may grow as entries are added to them. A table is made up of 3 parts:

* The table itself - 36 bytes
* 'List' entries - Those with consecutive integer indexes starting at 1 - 16 bytes each
* 'Map' entries - Those with non-consecutive integer indexes, and string indexes.- 40 bytes each

An empty table is just the minimum 32 bytes. As you start adding entries then it will begin to accumulate memory in which to store those. Memory accumulation isn't linear however, instead there is an exponential algorithm, so that as the table gets larger, incrementally larger numbers of elements are pre-allocated.

For example, the size of a list of numbers increases as follows as new values are inserted: 36, 52, 68, 100, 100, 164, 164, 164, 164, etc..

Tables which mix both forms of values (list entries, and map entries) use a mix of the two entry types

In Lua 5.1 tables that are created with literal initializers such as x = { "a", "b", key = "value" } allocate exactly what they need without any extra pre-allocation.