When you sit at the counter and order nigiri a la carte, they will come out in pairs.* There is nothing wrong with counting these in the regular Japanese way “ikko,” “niko.”
*It is said that nigiri-sushi in the Edo period was bigger than it is today, and too big to eat in one bite. In the Meiji period, the custom emerged of splitting this one big portion into two to make more easily consumed portions, and this is why it is common to get sushi in sets of two. However, nowadays making one piece of nigiri-sushi at a time is not very efficient. We think it’s actually easier for the sushi restaurant to make them in sets of two. Of course, you can order them one by one.
But the sushi restaurant won’t count them like that. Formally, sushi is counted in this way: Ikkan (one), Nikan (two).
We have absolutely no idea where the custom of using the “kan” counter came from. It’s also not clear when use of that counter for sushi started.
Of course, there are theories. For example, there is a theory that back at a time when a single unit of money was called “kan.” The price for one piece of sushi was around 1 ‘kan’, and the counting method gained popularity. There is another theory that one sushi roll was counted with the counter for roll “巻” (also pronounced “kan”), then a different kanji was used for it later. However, these are just theories that were created after the fact and the mystery remains unsolved.
Even if you ask the owner of a sushi restaurant, they’ll probably cock their head to one side, think for a moment, and tell you that the “kan” mystery may never be solved.
Sushi rolls wrapped in seaweed rolls are counted in units of 本 (hon/bon/pon) in the wrapped state, and when cut with a knife, the units change to 切れ (kire). While these units are fairly straight-forward for Japanese language speakers and easy to understand, only the enigmatic 貫 (kan) remains a mystery.
We hope this information will be helpful.
Revision date: April 29, 2020