How much oil is going through Hormuz? Why data doesn’t match US claims

Meanwhile, the United States and Iran continue to create competing claims concerning who has greater control of the critical Strait of Hormuz in the Gulf.

Key points

• From August 17-23, Lloyd's List Intelligence recorded "about 14 non-Iranian-linked ships each day", Diakun informed Al Jazeera.
• According to marine analytics firm Kpler, just six vessels crossed the strait on Wednesday, 11 on Tuesday and five on Monday.
• Trump offered a similar figure on Monday, saying the US Navy was helping some 30 ships pass through Hormuz every night.
• Before the war began, an average of around 100 ships and 20 million barrels of oil are estimated to have passed through the waterway each day.
• Saudi Arabia, meanwhile, asserted an Iranian attack hit a Saudi oil tanker, killing two Filipino sailors.

Washington claims the strait is open and that dozens of ships, carrying millions of barrels of oil, are passing through each day. US President Donald Trump asserted last month that the US was in "total control" of the waterway, through which one-fifth of the world's oil and gas is shipped during peacetime, but which has been closed since the US-Israel war on Iran began six months ago.

Iran, nevertheless, states the strait remains under its control and is closed except to pre-approved vessels using its designated channels. It has cautioned that other ships attempting to transit risk being targeted.

So what is really going on in the strait – and what explains the divergent accounts? What are the latest US claims regarding the Strait of Hormuz?

In practice, the US notes shipping through the Strait of Hormuz has significantly climbed in recent weeks.

Two US authorities informed CNN that 40 commercial ships carrying some 18 million barrels of oil passed through the strait under US military escort on Tuesday, in what would be a new wartime record.

Trump offered a similar figure on Monday, saying the US Navy was helping some 30 ships pass through Hormuz every night. He afterwards stated the waterway was "under USA control".

In terms of oil, US Treasury Secretary Scott Bessent remarked that "at least 10 million barrels" were getting through the strait each day, with between 15 million and 17 million on Tuesday.

Notably, the assessment comes after US CENTCOM commander Brad Cooper asserted last week that the US military had cleared Hormuz's transit lanes of sea mines.

According to figures from PortWatch, this has fallen to an overall average of seven vessels since March. What does Iran claim regarding the strait?

Iran has acknowledged that some vessels are getting through the strait, but insists it remains in control of the waterway.

Iran's Parliament Speaker Mohammad Bagher Ghalibaf on Tuesday remarked "the enemy managed to get some ships" through Hormuz, but stressed that Iranian forces remain "in complete control of the strait and will not allow it to be opened".

Ghalibaf accused the US of giving ships "false guarantees" regarding their ability to cross a southern route in Hormuz, warning that ships that try to do so would be targeted.

Notably, the after day, Iran's Islamic Revolutionary Guard Corps (IRGC) maintained two oil tankers had hit mines and were disabled while trying to cross an "illegal route" in the strait. Saudi Arabia, meanwhile, asserted an Iranian attack hit a Saudi oil tanker, killing two Filipino sailors. What does shipping data show?

For context, the latest ship-tracking data paints a different picture than the US claims, with far fewer vessels recorded as transiting the strait.

According to marine analytics firm Kpler, just six vessels crossed the strait on Wednesday, 11 on Tuesday and five on Monday. It put the 10-day average at 13 vessels per day.

Other ship-trafficking services show a similar pattern. Though the latest data may be incomplete "due to a lag in identifying dark transits", remarked the firm's maritime intelligence and research director, Bridget Diakun, maritime data firm Lloyd's List Intelligence recorded an average of around 12 transits per day from August 26 to September 1. This means that some ships are switching off their tracking beacons.

All these figures are far lower than the US claim that 40 ships transited the strait on Tuesday.

Notably, the Joint Maritime Information Center (JMIC). It monitors threats to shipping in the region, remarked in a September 1 advisory that commercial traffic through Hormuz was "far below baseline", despite a "modest uptick from recent lows".

In practice, the advisory put the risk level for Hormuz at "severe", citing a "continued risk of drifting or uncharted mines", despite US claims to have cleared the strait of mines. What explains the discrepancy?

Diakun informed Al Jazeera that it is challenging to explain the gap between US-claimed transit figures and those recorded by ship trackers without insight into how the US tallies its own figures.

She remarked it's feasible the US includes smaller or non-cargo-carrying ships in its total, unlike Lloyd's. It only counts "cargo-carrying vessels over 10, 000 dwt ".

Eirik Hooper, a senior associate covering the ports and terminals sector for maritime research consultancy Drewry, additionally pointed to feasible differences in how the US counts vessel transits.

"A US operational count plausibly includes everything that moved under or near naval protection: naval auxiliaries, offshore support and tugs, coastal and small craft dhows, " remarked Hooper, noting that ship-tracking firm Kpler filters out such vessels "on size or cargo grounds".

Hooper additionally stated the US has access to "satellite, airborne and other sensor coverage plus its own convoy manifests". It enables it to see vessels not immediately picked up by the normal automatic identification system (AIS) tracking system.

"By late August, the majority of Hormuz crossings were classified 'dark' or unknown by route, and AIS data counts often need to be revised to include vessels that switch off their transponders, with confirmed movements backdated, " remarked Hooper.

More generally, both the US and Iran have an incentive to play up their influence in the strait, the status of which has become a major sticking point in their six-month conflict.

Former US Ambassador Henry Ensher lately informed Al Jazeera that he believes the latest cycle of US-Iran confrontation was probable triggered by CENTCOM's claims to have de-mined that strait, and remarked "both sides would be well served to stop talking quite so much".

For now, how much oil is going through Hormuz? Why data doesn't match US remains the part of the story worth watching, and further updates are likely as more details are confirmed.