The rate a unit is converted is half of the units conversion rate to the conversion rate. For example, a Greek Priest has a conversion rate of 10. Therefore units will take 5 to 10 seconds to be converted.
Converting a garrisoned unit such as the Babylonian Siege Tower will also convert all units inside. You can convert enemy Priestess of Ra and use them to empower your buildings, or Babylonian Ox Carts and use them as storehouses.
The only unit that can convert buildings is the Priest of Ptah. The only unit that can also convert multiple units and buildings is also the Priest of Ptah.
Units that can convert units
Upgrades that can affect conversion