The stat has been raised frequently of late that 20% of the world's oil floes through the Straight. My understanding is that its 20% of total oil , but that around half of all oil production is used domestically where it is produced and never enters global markets. Unless I missed something when fact checking that, Iran is capable cutting off 40% of all purchasable oil.
There are several issues with that math. To begin with, it assumes that oil currently used domestically isn't on the market, but what do you expect oil producers to do if foreign buyers make a higher bid for the "domestic" oil? Or to put it another way, there's a reason the market price goes up by essentially the same amount in the oil-producing countries as everywhere else. Then it assumes that oil that currently go…
Pipeline capacity to the west is pretty limited. The connection via Syria is affected by the war aftermath, the Iraq/Turkey route is already at capacity, and the Saudi connection to the Red Sea is vulnerable to resumption of Houthi attacks. There's some connectivity via Oman, but that's largely natural gas rather than oil.