What happens if the Strait of Hormuz is blocked

The Strait of Hormuz is a 33-kilometre-wide passage between Iran and the Musandam peninsula of Oman. On a normal day, roughly 60 vessels pass through carrying about 21 million barrels of crude — around one-fifth of the world's daily seaborne oil. Right now, Brent is at $98.29 per barrel; 26 commercial vessels are in transit through the strait window; our verdict reads RESTRICTED.

A "blockade" of the Strait of Hormuz is a single phrase covering at least four operationally distinct scenarios: a credible threat that suspends commercial transits without firing a shot, a mining campaign that closes the channel by physical risk, declared military closure by Iran, or attrition through small-boat and anti-ship-missile harassment. The market response begins long before barrels stop moving — typically when major underwriters re-list the Gulf as a high-risk area and the war-risk insurance multiple jumps from its peacetime baseline of roughly 1× into the 2–4× band that container lines treat as their suspension trigger.

The price shock arrives first.

Brent typically spikes 15–40% on credible closure threats and more on confirmed disruption. The 1990 Gulf War saw a near-doubling within weeks; the September 2019 strikes on the Abqaiq facility — which never closed the strait but knocked out ~5 million barrels per day of Saudi production for a few hours — produced the largest single-day Brent move on record. The crucial point is that a Hormuz price shock is global. There is no escape route through domestic supply: even the United States, which is functionally self-sufficient on crude, prices its products against Brent.

Then the freight market freezes.

VLCC charter rates respond to closure scenarios faster than crude does, because tanker supply is fixed in the short run and demand for Cape-route capacity rises immediately. The combination of higher charter cost, higher bunker cost, and longer voyage times produces a freight-rate spike that is, in dollar terms, often larger than the headline Brent move. Insurance multiples lock that in: war-risk premiums on a single VLCC can move from $125,000 per voyage in peacetime to $2–3 million during a confirmed closure. Above 4×, the trade press says the route is "effectively priced out" — and that is the level at which container lines start announcing Cape reroutes.

The LNG crisis nobody talks about.

Unlike oil, LNG requires specialised infrastructure at both ends — liquefaction plants, cryogenic tankers, and regasification terminals. You can't just pipe it somewhere else. About a quarter of seaborne LNG transits Hormuz, almost all of it Qatari. Japan, South Korea, India, and the European Union are the main buyers; for some, Qatari volumes are still a third of total LNG imports. The substitution path runs through US Gulf-Coast cargoes and Australian volumes, but neither has the spare capacity to absorb a full Hormuz outage. A sustained closure therefore lands on Europe as a gas-price shock larger and stickier than the oil shock that accompanies it.

Bypass capacity is real, but partial.

Three pipelines route Gulf crude around the strait. Saudi Arabia's Petroline (East-West) carries up to 5 million barrels per day to Yanbu on the Red Sea. The UAE's ADCOP line carries up to 1.5 million bpd to Fujairah. Iran's Goreh-Jask line carries a fraction of its 0.35 mbpd nameplate to its Indian-Ocean coast. Combined nameplate bypass is roughly 7 mbpd against normal Hormuz flow of 17 mbpd. Strategic petroleum reserves add roughly 5–7 mbpd of additional release capacity for 30–60 days. The arithmetic is unforgiving: a sustained closure cannot be replaced; it can only be cushioned.

How long does the cushion last?

At maximum drawdown, IEA-coordinated reserves cover roughly 25–35% of the Hormuz shortfall for somewhere between 40 and 60 days. After that, demand destruction and accelerated bypass-pipeline utilisation must close the gap. The 1990–91 episode is the useful precedent: that crisis reduced Gulf output and Hormuz flow for months, and the world economy absorbed it through a combination of stockpile release, demand response, and substitution from non-Gulf producers. The 2026 economy is more oil-efficient per unit of GDP than the 1991 economy was, but it is also far more energy-intense in absolute terms.

Mutual exposure is what makes the threat unsustainable.

The often-repeated point about Hormuz is that the producers most capable of closing it depend on it most. Iran ships almost all of its sanctioned crude through the strait. Qatar has no overland alternative for any of its LNG. Iraq, Kuwait, and Bahrain are materially exposed to a closure they could not unilaterally end. Saudi Arabia and the UAE have partial bypass but lose most of their export capacity in a closure they did not start. That mutuality — every producer needing the strait open as much as every consumer does — is what has historically made the closure threat credible as a coercive lever and unsustainable as an actual posture.

What to watch.

• The war-risk insurance multiple — the cleanest single signal.
• Carrier announcements: Maersk, MSC, CMA CGM, Hapag-Lloyd, ONE, COSCO, Evergreen, HMM, ZIM.
• AIS transit count against the 60-vessel-per-day baseline.
• Petroline and ADCOP utilisation reported by Saudi Aramco and ADNOC.
• SPR draw announcements from the US, IEA member states, and China.
• The Brent–WTI spread: a widening spread means the disruption is being priced as Gulf-specific.

For a continuously updated assessment, see the live tracker. Country-by-country exposure is at /regions. SPR drawdown math is at /strategic-petroleum-reserves.