What does this number measure?
The Amazon drains a vast South American basin and receives many major tributaries before reaching the Atlantic. Its discharge is exceptional. The length of 6 400 km is a conventional reference: the choice of source, route and mouth varies between studies. This value does not settle a length ranking against the Nile.
This length follows the course adopted by the catalogue. Maps show simplified, sometimes partial courses; an independent bar represents the documented length, distinct from straight-line distance.
Compare the stated dimensions
The comparison uses the number in each fact sheet: altitude, height, diameter, length or distance, depending on the reference. Two values in metres do not necessarily describe the same property.
Source and limitations
Length is debated; some studies propose more than 6 900 km depending on the sources and routes adopted. The 6 400 km reference is not a definitive measurement.
Top view of a simplified geographic outline of the Amazon, based on the available mapped segments. The locator drawing may be partial, and river systems may combine several branches. The channel width and the textures of the water and banks are interpreted; this is not a satellite photograph. Only the lower bar represents the reference length documented by the source; the width of the map above does not measure that length. Outline: Natural Earth, public domain. Licence: Public domain.