The Strait of Hormuz connects the Persian Gulf to the Gulf of Oman and thence to the Arabian Sea and Indian Ocean. It is the single most strategically consequential maritime choke point in the world: approximately 20% of global oil consumption and roughly one-third of world LNG passes through the Strait every day. Bordering states are Iran to the north and Oman (Musandam peninsula) to the south. The shipping lane runs through Omani territorial waters — but Iran maintains capable naval and paramilitary forces on its northern shore and has demonstrated the will and capability to seize merchant tonnage.
Geography
Length. Approximately 90 nm (167 km) narrows section between Ra's Musandam (Oman) and the Iranian coast.
Width. Narrowest point ~21 nm (39 km). Two-way traffic separation scheme with two 2-nm-wide traffic lanes separated by a 2-nm buffer, occupying the Omani side of the Strait.
Depth. 60-100 m — deep enough for the largest laden VLCCs.
Bordering states. Iran (north), Oman + UAE (south). Ra's Musandam is the Omani exclave that provides most of the southern shore.
Traffic volume and cargo
Daily throughput: 21+ million barrels of crude and refined products, plus ~90% of world LNG produced in Qatar and increasing volumes of LPG. Major exporters loading in the Persian Gulf are Saudi Arabia (Ras Tanura, Yanbu), UAE (Ruwais, Fujairah, Zirku), Kuwait (Mina al-Ahmadi), Iraq (Basrah), Iran (Kharg Island), Qatar (Ras Laffan LNG), and Bahrain (Sitra). Any sustained closure would immediately affect world oil and gas prices; the strategic significance is difficult to overstate.
UNCLOS transit passage regime
The Strait of Hormuz is a strait used for international navigation under UNCLOS Part III. All ships (including warships and submerged submarines) and aircraft have the right of transit passage — a stronger right than innocent passage. Iran and Oman may exercise limited jurisdiction (safety of navigation, pollution, fishing) but cannot suspend or hamper transit. Iran signed UNCLOS but has not ratified; it maintains a controversial interpretation that the transit passage right is only available to states party to the Convention. This interpretive dispute has occasionally been cited as justification for Iranian interference with third-state vessels.
Iranian seizure history
The Iranian Islamic Revolutionary Guard Corps Navy (IRGCN — distinct from the regular Iranian Navy) has repeatedly detained merchant tonnage in and near the Strait. Not all detentions are UNCLOS-consistent; the pattern often reflects broader Iran-West geopolitical events.
Grace 1 / Adrian Darya (2019). Iranian-flagged VLCC crude tanker seized by UK Royal Marines off Gibraltar; retaliation-seizure of UK-flagged Stena Impero.
Stena Impero (2019). UK-flagged product tanker boarded and held by IRGCN in the Strait of Hormuz. Held for 2 months; crew including Indian, Filipino, Latvian, and Russian nationals.
MT Merchant Marine + others (2015-2019). Multiple limpet-mine attacks off Fujairah + Gulf of Oman attributed to Iran during 2018-2019 tanker war.
MSC Aries (2024). Container ship seized by IRGCN helicopter boarding at the entrance to the Strait; 25 crew held. Released May 2024. See /piracy-incidents/msc-aries-2024-04-13.
Threat + contingency routing
Unlike the Bab-el-Mandeb, the Strait of Hormuz has NO ready contingency route: Persian Gulf crude and LNG MUST transit the Strait to reach world markets. Alternatives:
Saudi East-West Pipeline. ~5 million barrels/day capacity from eastern Saudi fields to Yanbu on the Red Sea, bypassing Hormuz.
UAE Habshan-Fujairah Pipeline. ~1.5 million barrels/day capacity from Abu Dhabi to the port of Fujairah on the Gulf of Oman side of the Musandam peninsula.
Iraq-Turkey Pipeline (Kirkuk-Ceyhan). ~1.6 million barrels/day capacity from northern Iraqi fields to the Mediterranean coast of Turkey. Frequently disrupted; capacity substantially unused.
Iran (theoretical). Iran maintains the Neka-Tehran pipeline for Caspian import + Bandar Jask export terminal for southern crude — but Iranian export volumes are constrained by sanctions.
Total bypass capacity is a fraction of the ~21 million barrels/day daily throughput. A sustained closure of the Strait would be a major global energy-market disruption within days.
War-risk premiums + JWC listing
The Joint War Committee (JWC) of Lloyd's and IUA has consistently listed the Persian Gulf, Strait of Hormuz, and Gulf of Oman as high-risk areas. Vessels transiting the JWC-listed area must notify hull & machinery war-risk underwriters and pay additional-premium (AP) rates. AP levels vary with geopolitical tension: baseline 0.02-0.05% of hull value, spiking to 0.15-0.30% during high-tension periods (post-Stena Impero 2019, post-MSC Aries 2024). Cargo war-risk cover is separately quoted.
Master's procedural checklist for Hormuz transit
Register the transit with UKMTO 24-48 hours in advance.
Monitor UKMTO advisories + the ICS Anti-Piracy Guidance for the region.
Maintain the vessel in the Traffic Separation Scheme where possible; avoid Iranian territorial waters.
Maintain heightened bridge watchkeeping; brief the crew on evasion procedures under BMP5 anti-piracy guidance.
Have citadel + panic-button + AIS-toggle protocol reviewed with the Master and DPA before the transit.
Verify P&I + war-risk cover is current and the vessel is on the underwriter's approved routing.
In the event of hostile approach: activate SSAS, notify UKMTO immediately, follow BMP5 evasion.