Do I recite out loud or silently in prayer?

Which prayers are loud and which are quiet

• Fajr (2 rakat): out loud in both.
• Dhuhr (4) and Asr (4): silent in all rakat.
• Maghrib (3): out loud in the first two, silent in the third.
• Isha (4): out loud in the first two, silent in the last two.
• Jumu'ah and Eid prayers: out loud.

This pattern comes from how the Prophet ﷺ prayed. Abu Hurairah said that in every prayer there is recitation: what the Prophet ﷺ let them hear, they let others hear, and what he kept quiet, they kept quiet (Sahih al-Bukhari 772). The opening takbir, "Allahu Akbar" between positions, and the final salam are said audibly by the imam in every prayer. See What do Muslims say when they pray?

"Out loud" means moderate, not shouting

Allah taught a middle way in the Quran:

So "loud" means a clear voice that you and those near you can hear. "Silent" means a whisper you can hear yourself, or at least moving your tongue and lips. Most scholars say just thinking the words without moving your mouth does not count as recitation.

If you pray alone

When you pray Fajr, Maghrib or Isha alone, scholars differ. The Shafi'i and Hanbali schools recommend reciting aloud as the imam would; the Hanafi school lets you choose. Either way, keep it gentle, especially if family members are sleeping. Women praying alone or with other women can recite aloud too, and many scholars advise lowering the voice when unrelated men are close by.

Behind an imam and in voluntary prayers

• Behind an imam: you stay quiet in loud prayers and listen. Whether you also recite al-Fatiha under your breath is a known difference of opinion. See Why is Surah al-Fatiha in every prayer?
• Night and voluntary prayers: you can recite aloud or quietly, whichever helps you focus.
• Daytime voluntary prayers: usually quiet.