It varies a lot, depending on whether it's rainy or dry season, in a relatively rainy or dry year. And where you measure (in the mountain origins or where it empties into the sea).
The average width, in the rainy season, has been cited as 25 miles. In the dry season, the mouth of the river (where it empties into the Atlantic) is still at least 7 miles wide.
The Nile River (in North Africa) is longer, but the Amazon carries more water. It empties a shocking percentage of the fresh water that flows into the world's oceans, each year. At any one time, on average, it's thought that the Amazon River holds 20% of the world's fresh water (not frozen).
The average width, in the rainy season, has been cited as 25 miles. In the dry season, the mouth of the river (where it empties into the Atlantic) is still at least 7 miles wide.
The Nile River (in North Africa) is longer, but the Amazon carries more water. It empties a shocking percentage of the fresh water that flows into the world's oceans, each year. At any one time, on average, it's thought that the Amazon River holds 20% of the world's fresh water (not frozen).