I was trying to find a list of the lengths of the Great Rivers of Middle-earth

It would be interesting to see some size comparisons between the Great Rivers of Beleriand like Sirion and Gelion and the ones of Middle-earth in the Third Age. There are different maps showing how Beleriand and Third Age Middle-earth were connected, but I understand there is no canon version. That makes comparisons based on those maps difficult.

From wikipedia I learnt that Karen Wynn Fonstad estimates Anduin to be 2,233 km, I wonder if there are more estimates or even direct mentions of their length in Tolkien's literature.

  • 2
    One can probably guess from looking at the maps, but it's probably the Anduin.
    – Edlothiad
    Sep 19, 2018 at 19:10
  • Have you checked en.wikipedia.org/wiki/List_of_Middle-earth_rivers (en.Wikipedia article)? It generally doesn't give length, but is still a useful starting point.
    – b_jonas
    Sep 19, 2018 at 19:40
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    Just to be clear, this information almost certainly doesn't exist for most rivers explicitly in the Legendarium. One would have to use a thumb and measure the rough length of measures from assumed sources to mouths.
    – Edlothiad
    Sep 19, 2018 at 20:13
  • 1
    Anduin was often called the great river. This site describes it as the Great River of Wilderland and the longest river in the Third Age. en.wikipedia.org/wiki/Anduin I find it quite easy to believe that there could have been longer, wider, or stronger flowing rivers somewhere in Arda sometime during the fictional history of Middle-earth (for example, the Mississippi and the Amazon might already exist in the New lands after the Fall of Numenor), but as far as I can tell Anduin was the longest river in any part of Middle-earth that was well mapped at any stage of history. Sep 20, 2018 at 19:08
  • according to this map of Beleriand the river Gelion was longer than the river Sirion, though the full length of Gelion is not shown. Sep 20, 2018 at 19:13

1 Answer 1


The three longest rivers mentioned in Tolkien's legendarium are Anduin, Sirion, and Gelion. One of the problems with finding a good estimate is that The Silmarillion's maps have no scale, so it's nigh impossible to calculate distance. However, it is possible to get a rough estimate on the order. Tolkien writes in The Silmarillion that Gelion is "...twice as long as Sirion," (p. 123). Map of Beleriand Tolkien also writes, "From the meeting of [Gelion's] arms he flowed south for forty leagues before he found his tributaries," (p. 123). Using this quote together with the map of Beleriand, we can get a solid estimate at the length of Sirion and Gelion and compare these to the estimates of Anduin by Karen Fonstad. On the map, the distance between those two points is 1 3/4 inches. (I'm American, I use inches. Sorry!) So by that scale, 1 3/4 inches on the map equals 40 leagues in universe. A league is approximately 3 miles, so 1 3/4 inches = 120 miles, and 1 inch equals about 68.57 miles. To estimate the length of Sirion, we have to measure its length as the crow flies from Eithel Sirion to the Mouths of Sirion; we find that this equals 5 1/2 inches. 68.57 * 5.5 = 377.35 miles for the length of Sirion. Gelion is twice that, so 377.35 * 2 = 754.27 miles long. Both of these are dwarfed by the estimated length of Anduin, at 1,388 miles long. So, the final answer is:

  1. Anduin - 1,388 miles
  2. Gelion - 754.27 miles
  3. Sirion - 377.35 miles

Note: This system can be used to measure any river on this map.

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