Meaning of ‘Qul Huwallahu Ahad’ Being Equivalent to One-Third of the Quran
Question

Answer #4156 item#2, then there is no need to learn the entire Quran or to even read it during Ramadan, etc. All you have to do is to read surah Al-Ikhlas. I think you made a mistake. Surah Al-Ikhlas is the substance of 1/3 of the Quraan. It is amazing to believe that reading the surah al-Ikhlas 3 times will give you the blessing of reading the ENTIRE Quran, then there is no point reading the entire Quran.
Praise be to Allah.Hadiths about Qul Huwallahu Ahad being one-third of the Quran
There follow some of the ahadith narrated from the Prophet (peace and blessings of Allah be upon him) which state that Surat al-Ikhlas (Qul Huwa Allahu Ahad) is equivalent to one-third of the Quran.
 Al-Bukhari (6643) narrated from Abu Sa’id that a man heard another man reciting Qul Huwallahu Ahad and repeating it. The next morning he came to the Messenger of Allah (peace and blessings of Allah be upon him) and told him about that. The man thought that it was too little, but the Messenger of Allah (peace and blessings of Allah be upon him) said: “By the One in Whose Hand is my soul, it is equivalent to one-third of the Quran.”
Muslim (811) narrated from Abu’l-Darda that the Prophet (peace and blessings of Allah be upon him) said: “Is any one of you unable to recite one-third of the Quran in one night?” They said, “How could anyone read one-third of the Quran?” He said, “Qul Huwallahu Ahad is equivalent to one-third of the Quran.”
 Muslim (812) narrated that Abu Hurayrah said: The Messenger of Allah (peace and blessings of Allah be upon him) said: “Gather together, for I will recite to you one-third of the Quran.” So those who could gather together gathered there, then the Prophet of Allah (peace and blessings of Allah be upon him) came out and recited Qul Huwa Allahu Ahad, then he went in. They said to one another, perhaps there has been some news from heaven on account of which he has gone inside (the house). Then the Prophet of Allah (peace and blessings of Allah be upon him) came out and said, “I told you that I was going to recite to you one-third of the Quran. Verily it is equivalent to one-third of the Quran.” 
The bounty of Allah is immense 
The bounty of Allah is immense, and Allah has bestowed His bounty upon this ummah and has made up for its short life span by giving it more reward for simple deeds. It is strange that with some people, instead of this motivating them to do more good, this makes them apathetic and lazy in doing acts of worship, or they feel that this bounty and reward is strange and farfetched.
How Qul Huwallahu Ahad  is equivalent to one-third of the Quran
There is a difference between jaza (reward) and ijza (what is sufficient). What is making the brother confused is that he does not see the difference between them.
 Jaza means the reward which Allah gives for obeying Him.
 Ijza means what is sufficient and takes the place of something else.
Reciting Qul Huwallahu Ahad brings a reward equivalent to reciting one-third of the Quran, but it does not take the place of reading one-third of the Quran.
 If a person vows – for example – to read one-third of the Quran, it is not sufficient for him to read Qul Huwallahu Ahad, because it is equivalent to one-third of the Quran in reward, but not in terms of being sufficient or taking the place of reading one-third of the Quran.
 The same may be said of reciting it three times. If a person recites it three times in his prayer,  that does not mean that he does not have to recite al-Fatihah, even though he will be given the reward of reciting the whole Quran.
 A similar example is the reward given by the Lawgiver to one who offers a single prayer in the Sanctuary of Makkah, and that he will have the reward of one hundred thousand prayers. Does anyone take this divine bounty to mean that he does not have to pray for decades because he offered a single prayer in the Haram that is equivalent to one hundred thousand prayers?
 Rather this has to do with reward; as for what is sufficient, that is another matter altogether.
 Moreover, none of the scholars has ever said that there is no need for us to read the Quran or that Qul Huwallah Ahad is sufficient and takes the place of that. 
Why Qul Huwallahu Ahad  is equivalent to one-third of the Quran 
The correct scholarly view is that this surah has this great virtue because the Quran deals with three topics: one-third for rulings, one-third for promises and warnings, and one-third for the Divine names and attributes.
 This surah combines names and attributes.
 This is the view of Abu’l-‘Abbas ibn Surayj, and Shaykh al-Islam Ibn Taymiyah stated that it was good in Majmu’ al-Fatawa, 17/103.
 The Muslim cannot do without the two other issues, which are the rulings and the promises and warnings. His knowledge cannot be complete unless he looks at the Book of Allah as a whole. The one who stops at Surat al-Ikhlas cannot know the other two matters.
 Shaykh al-Islam (Ibn Taymiyah – may Allah have mercy on him) said:
"Rewards are of different types, just as wealth is of different types, such as food, drink, clothing, houses, money and so on. If a man possesses one type of wealth, to the value of one thousand dinars, that does not mean that he can do without the other types. Rather if he has wealth in the form of food, he also needs clothing and a place to live, etc. Similarly if it is a type other than money, he still needs other things. If he has nothing but money, he will need all kinds of wealth that are usually needed. In al-Fatihah there are the benefits of praise and du’a which people need, and Qul Huwa Allahu Ahad cannot replace it in that sense. Although its reward is very great, he cannot benefit from it unless he also recites the Opening of the Book (al-Fatihah) in his prayer. Hence if a person recites only Qul Huwa Allahu Ahad in his prayer, without al-Fatihah, his prayer is not valid. Even if he recited the whole of the Quran without al-Fatihah, his prayer would not be valid, because al-Faatihah refers to the basic needs that people cannot do without.” (Majmu’ al-Fatawa, 17/131)
 And he said:
“The people need the commands, prohibitions and stories that are in the Quran, even though Tawhid is greater than that. Man needs to know what he is enjoined to do and what he is forbidden to do; he needs to know what is enjoined upon him and the stories and promises and rewards. These cannot be replaced by anything else, and Tawhid cannot be replaced by these. The stories cannot take the place of the commands and prohibitions, and the commands and prohibitions cannot take the place of the stories. Rather everything that was sent down by Allah is beneficial and people need it.
 If a person recites Qul Huwallahu Ahad, he earns a reward equivalent to the reward of one-third of the Quran, but that does not mean that the reward is of the same kind as that earned by reading the rest of the Quran. Rather he may need the kind of reward that comes from reading the commands and prohibitions and stories, so Qul Huwa Allahu Ahad cannot take the place of all that.”  
And he said:
“The knowledge that is to be gained by reading the rest of the Quran cannot be gained by reciting this surah only. So whoever reads the whole Quran is better than one who simply recites this surah three times in the sense that he earns different kinds of reward, even though the one who recites Qul Huwa Allahu Ahad earns a reward equivalent to that reward, but it is of one type and does not include all the types that a person needs. This is like a man who has three thousand dinars and another who has food, clothing, accommodation and money equivalent to three thousand dinars.  The latter has that which will benefit him in all his affairs, whereas the former needs what the latter has, even though what he has is equivalent in value. Similarly, if he has the finest food, equivalent to three thousand dinars in value, he still needs clothing and accommodation, and weapons and tools that will ward off harm from him, and the like, which cannot be done with food alone.” (Majmu’ al-Fatawa, 17/137-139)
 And Allah knows best.