how to check row size in encrypted table

1) Situation: I use sqlitecipcher for Android, kindly provided by commonsguy as a library module to store text in an encrypted database

2) Requirement: I need to inform the user about how much space an entry ("entry" should be read here as "database table row") takes on the disk

As far as I know, SQLite (and thus the sqlitecipher wrapper) does not provide an API to check the size of a row, and checking the byte count after reading an entry will give the size of non-encrypted text, so that information would be incorrect.

Of course I could AES the data again and check the size, but this would be a HUGE waste of processing power.

Are there any reliable formulas that allow to calculate how the amount of chars changes after the text is AES-encrypted? Or any other suggestions how to check the row size of an encrypted table?