What to do if you forget what rak’at you’re in during salah? If it is the first time it has happened to you, then you can break your salah and start again. 

However, if it keeps happening to you, then you base it on the least. So if it is between 2 and 3 then you just assume you have done 2 and pray the third. 

Dr. Mufti Abdur-Rahman ibn Yusuf answers.