Short answer
The shahada makes someone Muslim when they say it by choice, understanding its basic meaning, believing it in the heart and accepting Islam as a whole. Many teachers list seven conditions: knowledge, certainty, acceptance, submission, truthfulness, sincerity and love. These describe true faith; they are not an exam to pass before you may say it.
In the Hanafi school, iman is belief (tasdiq) in the heart with affirmation by the tongue for one who is able to speak. The shahada must be said by choice, its meaning known and believed, without holding on to any belief that contradicts it. Hanafi jurists add that a Jew or Christian should also disown beliefs contrary to Islam, which the shahada already implies.
The four schools agree on this.
Explanation
The shahada, there is no god but Allah and Muhammad is the messenger of Allah, is the first pillar of Islam and the door into it. Everything else, prayer, fasting, zakat and Hajj, rests on it. That is why scholars took care to explain what makes it real.
The seven conditions taught in many mosques today were gathered by later scholars from the Quran and hadith:
- Knowledge: knowing what it means, that only Allah deserves worship.
- Certainty: believing it without doubt.
- Acceptance: accepting it rather than rejecting any part of it.
- Submission: being willing to follow it in practice.
- Truthfulness: meaning it, not saying it falsely.
- Sincerity: saying it for Allah, not for gain or show.
- Love: loving Allah, His messenger and this faith.
The classical Hanafi creeds do not use this list, but they agree with its substance: faith is belief in the heart, confirmed by the tongue. The list is a description of complete faith. A new Muslim who believes and says the words is Muslim from that moment, and grows in these qualities over a lifetime.
What the shahada does not need: Arabic fluency (understanding the meaning in your own language is enough), witnesses, an imam, a certificate, or perfect practice first. See the shahada, how to convert and converting while you still struggle.
The evidence
Quran, Surah Muhammad 47:19
فَٱعْلَمْ أَنَّهُۥ لَآ إِلَٰهَ إِلَّا ٱللَّهُ وَٱسْتَغْفِرْ لِذَنۢبِكَ وَلِلْمُؤْمِنِينَ وَٱلْمُؤْمِنَٰتِ ۗ وَٱللَّهُ يَعْلَمُ مُتَقَلَّبَكُمْ وَمَثْوَىٰكُمْ ﴿١٩﴾
So know, [O Muhammad], that there is no deity except Allah and ask forgiveness for your sin and for the believing men and believing women. And Allah knows of your movement and your resting place.
Knowing the meaning of the shahada is the first condition.
Quran, Surah Al-Hujuraat 49:15
إِنَّمَا ٱلْمُؤْمِنُونَ ٱلَّذِينَ ءَامَنُوا۟ بِٱللَّهِ وَرَسُولِهِۦ ثُمَّ لَمْ يَرْتَابُوا۟ وَجَٰهَدُوا۟ بِأَمْوَٰلِهِمْ وَأَنفُسِهِمْ فِى سَبِيلِ ٱللَّهِ ۚ أُو۟لَٰٓئِكَ هُمُ ٱلصَّٰدِقُونَ ﴿١٥﴾
The believers are only the ones who have believed in Allah and His Messenger and then doubt not but strive with their properties and their lives in the cause of Allah. It is those who are the truthful.
True faith is free of doubt.
Sahih Muslim 26
Sahih... من مات وهو يعلم أنه لا إله إلا الله دخل الجنة ...
"Whoever dies knowing that there is no god but Allah will enter Paradise."
Knowledge of the shahada's meaning.
Sahih Muslim 27
Sahih... لا يلقى الله بهما عبد غير شاك فيهما ...
"No servant meets Allah with these two testimonies, without doubting them, except that he enters Paradise."
Certainty without doubt.
Sahih al-Bukhari 99
Sahih... خالصا من قلبه أو نفسه ...
"Whoever says there is no god but Allah sincerely from his heart."
Sincerity in saying the shahada.
Where the ruling is recorded
- al-Fiqh al-Akbar, the section on the definition of iman. Faith is affirmation by the tongue and belief in the heart.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Jihad, Bab al-Murtadd, on how a person becomes Muslim. Discusses disowning a former religion for Jews and Christians.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.