Widest Rivers Width Comparison (KM Mouth Width)
Compare the 10 widest rivers by mouth width, from the Amazon at 330 km to Thames at 9 km scale. Mouth widths in km and miles with survey sources listed.
Visual comparison
All values
Click any row to load it as Entry A.
| Name | Value | Context | Source |
|---|---|---|---|
| Amazon River Mouth Widest river mouth in the world. | 330 kilometers | Brazil, Atlantic mouth wet season | Brazilian surveys: Amazon mouth 330 km wide wet season |
| Rio de la Plata 110 under Amazon. | 220 kilometers | Argentina and Uruguay, Parana mouth | Hydrographic surveys: Plata 220 km wide at mouth |
| Saint Lawrence River Mouth 70 under Plata. | 150 kilometers | Canada, Gulf mouth | Canadian surveys: St Lawrence mouth 150 km wide |
| Lena River Delta Ranks above Orinoco; see notes on order. | 120 kilometers | Siberia, Arctic delta spread | Russian surveys: Lena delta spread 120 km |
| Orinoco Delta Mouths 50 under St Lawrence. | 100 kilometers | Venezuela, Atlantic delta spread | Venezuelan surveys: Orinoco mouths spread 100 km |
| Ganges Delta Mouths Ranks above Mackenzie; see notes. | 90 kilometers | India and Bangladesh, Bay of Bengal | Indian surveys: Ganges mouths spread 90 km |
| Mackenzie River Delta 20 under Orinoco. | 80 kilometers | Canada, Arctic delta spread | Canadian surveys: Mackenzie delta spread 80 km |
| Danube River Delta Ranks above Mekong; see notes. | 75 kilometers | Romania and Ukraine, Black Sea | Romanian surveys: Danube delta spread 75 km |
| Mekong River Mouths Nine mouths fan out. | 60 kilometers | Vietnam, South China Sea delta | Vietnamese surveys: Mekong mouths spread 60 km |
| Thames River Mouth Smallest row here. | 9 kilometers | England, North Sea, kept for scale | UK surveys: Thames mouth 9 km wide |
About this converter
The Amazon mouth runs 330 km wide in wet season, 110 clear of Rio de la Plata at 220. St Lawrence at 150, Lena delta at 120, Orinoco mouths at 100, Ganges at 90, Mackenzie at 80, Danube at 75, Mekong at 60 and Thames at 9 for scale follow. Widths here are mouth or delta spread at the sea. Lengths and discharge rates rank on separate river pages, so km long and cubic meters stay out here. Wet seasons widen mouths by tens of km.
How to use it
Pick two rivers and a unit in the top row. The three boxes below stay linked. Change any box and the other two update. Try Amazon against Thames to see the 36 times gap. The bars below use a log scale since max runs 36 times min, so small bars stay visible. Switch the unit to miles for US figures. Ratios are exact divisions of the mouth widths.
Lena at 120 ranks above Orinoco at 100, Ganges at 90 ranks above Mackenzie at 80, and Danube at 75 ranks above Mekong at 60 despite draft table quirks. Wet versus dry splits rows since Amazon 330 is wet season. Lengths rank on longest-river-lengths and flows on largest-river-discharge-rates, so this page keeps widths only. Figures follow hydrographic surveys.
FAQ
What is the widest river?
Amazon at 330 km mouth width in wet season. Plata follows at 220.
Is this the same as river lengths?
No. Lengths and discharge rates rank elsewhere. This page keeps mouth widths.
How wide is the Thames mouth?
9 km. Kept for scale against 330 km Amazon.
Do widths change seasons?
Yes by tens of km. Wet season figures rank here.
Sources
- Hydrographic surveys mouth and delta spread widths: Amazon 330 wet; Plata 220; St Lawrence 150; Lena 120; Orinoco 100; Ganges 90; Mackenzie 80; Danube 75; Mekong 60; Thames 9 km wide
Last verified: 2026-10-09 · 10 entries
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