Why the strait matters
The Bosphorus is the only way out of the Black Sea to the open sea. Ships from the ports of Ukraine, Russia, Romania, Bulgaria and Georgia pass through it and then the Sea of Marmara and the Dardanelles. The Bosphorus, the Sea of Marmara and the Dardanelles together are known as the Turkish Straits.
According to the US Energy Information Administration (EIA), an average of 3.3 million barrels of oil a day passed through the Bosphorus in 2024, more than half of it crude. The largest exporter of oil through the straits is Kazakhstan, which ships it through the CPC pipeline and the Russian port of Novorossiysk. Grain from Black Sea ports also goes through the Bosphorus.
According to Turkey's Ministry of Transport, about 40,000 ships a year passed through the Bosphorus in 2024–2025: 41,363 in 2024 and 40,172 in 2025, an average of about 110 a day.
How the strait is laid out
The Bosphorus runs for about 31 km, with Istanbul on both shores: the western shore is Europe, the eastern shore is Asia. At its narrowest, between Kandilli Point and Aşiyan, the strait is about 700 m wide. At Kandilli ships have to change course by 45° in a current of up to 7–8 knots, and at Yeniköy by 80°. The surface current runs from the Black Sea to the Sea of Marmara, while saltier water flows back near the bottom.
Three bridges span the strait, and the Marmaray rail tunnel and the Eurasia road tunnel run under it. Besides ships in transit, ferries and other local craft ply the strait all the time.
In November 1979 and March 1994 tankers carrying oil collided with other ships in the strait: the ships burned and dozens of seafarers died. In 1995 the IMO adopted rules for navigation in the Turkish Straits, and in December 2003 Turkey launched the Turkish Straits Vessel Traffic Service (VTS).
Rules of passage
Under the 1936 Montreux Convention, merchant ships pass freely through the strait in peacetime. A pilot is not compulsory, but according to Turkey's Ministry of Transport, about 60% of the ships that passed through the Bosphorus in 2025 took one. Large ships arrange their passage in advance. Turkey can bring in one-way traffic and stop traffic in fog or after an accident.
The convention lets Turkey restrict the passage of warships.
The war and the strait since 2022
- February 2022. Russia began its full-scale invasion of Ukraine. Turkey closed the straits to warships of the parties to the war, citing Article 19 of the Montreux Convention.
- March 2022. Fishermen found a drifting naval mine about 2 km from the northern entrance to the strait. The Turkish military defused it, and traffic in the area was briefly stopped.
- July 2022 – July 2023. The Black Sea Grain Initiative, brokered with Turkey's help, was in force; ships carrying grain were inspected off Istanbul. According to Reuters, nearly 33 million tonnes of grain left Ukraine's ports in that time. In July 2023 Russia withdrew from the deal.
- December 2022. Turkey began requiring tankers to prove they had insurance for the passage through the straits. About 20 tankers queued at the northern entrance to the Bosphorus.
- November 2025. Naval drones hit two tankers off Turkey's Black Sea coast; no injuries among the crews were reported. Ukraine's security service (SBU) reportedly claimed the strikes; Turkey condemned them.
- March 2026. A tanker carrying oil from Novorossiysk was attacked about 33 km from the Bosphorus; the crew was unhurt. No one claimed responsibility.
- July–August 2026. According to Reuters, Russia stepped up strikes on the ports of Odesa, Chornomorsk and Pivdennyi, and Ukraine stepped up attacks on ships serving Russian oil and grain exports. Damaged ships arrived at the Bosphorus under coast guard escort, and some ships passed through the strait with nets, water tanks and tyres hung over the side as protection against drones.
- September 2026. The London insurance market's Joint War Committee added almost the whole Black Sea to its war-risk area, except the territorial waters of Turkey, Bulgaria, Romania and Georgia. Until then, in the Black Sea, it covered only the waters of Russia and Ukraine.
- October 2026. Merchant ships were attacked, and some were sunk, in the exclusive economic zones of Romania and Bulgaria. The defence ministers of Bulgaria, Romania and Turkey condemned attacks on merchant ships in a joint statement.
Ship traffic in 2026
IMF PortWatch counts cargo ships and tankers from AIS signals. According to its data, an average of about 92 such ships a day passed through the Bosphorus in 2025. In the first half of 2026 it was about 86, against 91 a year earlier, and the decline accelerated from July: about 62 ships a day in August 2026 and about 51 in September.
What the map shows
The map shows the whole strait, from the Black Sea entrance to the Sea of Marmara. Ships wait at anchor off both entrances for their turn to pass, and ferries and local craft ply the strait all the time. Zoom out to see the Sea of Marmara and the approaches to the Dardanelles. Turkey's Directorate General of Coastal Safety (Kıyı Emniyeti) publishes official information on traffic in the strait.