Do not forget toilet paper!
Usually, in public toilets, there is no toilet paper. So, it’s best to have your own toilet paper. Also, know that there are no western toilets in public places and most toilets are squat toilets. (Most of hotels are equipped with western toilets).
Finding a toilet in Iran is not very difficult. If necessary, you can use the services of religious places (mosque and Imam Zadeh, etc.) and if you want to ask others, Iranians are familiar with the words “WC” and “toilet”.