How long is the Ob River? Length with the Irtysh
The Ob alone is about 3,650 km long, and with the Irtysh about 5,410 km (3,362 miles). It is the seventh longest river system in the world.
Lay the Ob over your country
The river and a country at one scale. Pick a country, drag the river or switch the globe to the Mercator map.
Ob-Irtysh: about 5,410 km (3,362 miles), about 1.4 times the straight-line distance from New York to Los Angeles (about 3,940 km).
Drag the river with your finger or mouse. It moves over the globe without changing shape or length, and its north stays up. The globe keeps the true proportions; on the Mercator map you can see how a river moved north grows.
Where the Ob flows
The most distant sources of the system lie in the Chinese part of the Altai, where the Black Irtysh begins. The Irtysh flows through Kazakhstan into Russia and joins the Ob on the West Siberian Plain. The Ob ends in the Gulf of Ob, an inlet of the Kara Sea about 800 km long.
The Ob basin covers about 2.98 million km², the sixth largest in the world. At its mouth the river carries about 13,000 m³/s of water on average.
Rivers of similar length, straightened
Rivers drawn at one scale. Straighten them to compare their lengths and see how they look on a Mercator map.
- Yellow River: about 5,464 km
- Ob-Irtysh: about 5,410 km
- Paraná: about 4,880 km
On a Mercator map: about 9,900 km
On a Mercator map the Ob looks about 9,900 km long (×1.83 its true length). Its course lies far from the equator, so the map stretches it by about 83%. On a globe and in the tables the difference disappears.
Open the Mercator mapHow long is it really?
About 5,410 km is the length of the Ob counted with the Irtysh as its upper course. The Ob alone, from the meeting of the Biya and the Katun in the Altai, is about 3,650 km, and the Irtysh alone about 4,248 km.
The line on this page's maps is about 4,561 km long, shorter than the sources say, because a 1:10 million map smooths the bends and the mouth. That is why lengths here come from the sources, not from the drawing.
Ob-Irtysh: questions and answers
The Ob alone is about 3,650 km long. With the Irtysh counted as its upper course it is about 5,410 km (3,362 miles) according to Encyclopædia Britannica.
The Irtysh (about 4,248 km) is longer than the Ob alone (about 3,650 km), even though it is the Ob's tributary. That is why the system is measured from the source of the Irtysh.
The Ob itself forms where the Biya and the Katun meet in the Altai. The most distant sources of the whole system lie in the Chinese Altai, where the Black Irtysh begins.
The Ob flows into the Gulf of Ob, an inlet about 800 km long of the Kara Sea in the Arctic Ocean.