Sunday, April 5, 2020

The Kezayis Post

With Pesach approaching, it's kezayis season again. The monograph that I wrote on the evolution of the kezayis, from the size of an olive to a matzah ten times that size, seems to be the most popular piece that I have ever published. If you haven't read it, you can download it at this link.

Here is a list of other posts relating to this topic:

Matzah/Maror Chart for Rationalists - so that you, too, can have a chart!

The Popularity of Olives - exploring why this paper is so popular and yet hated by some.

Why On Earth Would One Eat A Kezayis?  - discussing the strange notion that one should aim to eat a kezayis of matzah on Seder night.

The Riddle of the Giant Kezayis Defense - wondering why many people would not accept that a kezayis is the size of an olive.

Maniacal Dishonesty About Olives - exposing an error-ridden critique that appeared in the charedi polemical journal Dialogue.

It's Krazy Kezayis Time! - discussing the view that one should eat a huge amount of matzah in a very short time in order to fulfill all opinions.

The Kezayis Revolution - announcing the fabulous sefer by Rabbi Hadar Margolin, which presents the same arguments that I brought but in a more yeshivish manner. He also brings an astonishing array of evidence that many recent charedi gedolim likewise held that a kezayis is very small, including even the Chazon Ish! Best of all, the entire sefer can be freely downloaded.

"But It's Our Minhag/ Mesorah!" - examining a counter-argument for using the large shiurim.

Finally, two notes regarding The Biblical Museum of Natural History:

First, coronavirus has not stopped us from inspiring and educating people! We've been running live online tours for the last week, and they've been fantastic! You can sign up for our Pesach tours at As well as a brief "Highlights" tour, we also have six in-depth tours of different halls.

Second, we are really looking for people who support our goals of educating the entire spectrum of society about the relationship between Torah and the natural world, and who want to be part of our mission. To join the museum as a patron, please see for details. We can now arrange tax-deductible donations in Israel, the UK and Canada, as well as the US. For easy online donations, please click this link. Thank you for supporting our mission!


  1. If you're one of those people for whom finding out that an olive is the size of an olive is a gateway drug to a weird and wonderful world of Judaism that makes sense, please check out For those who saw it last Pesah, unfortunately, stuff came up this year and I wasn't able to get the 2nd draft out, but I did make a little bit of headway with the Reactionary Haggadah series.

  2. I have on good authority from Dovid Kornreich that if one eats a kezayis that's the size of an olive, one is well on his way to being a kofer in the whole Torah.

  3. In the seder-night it might seem attractive to use a smaller measure for kezayis. However, it is the whole year relevant for Brachas Achoronos, also for example if one eats more than 8 kezayis cake one hast to wash the hands and say Birkat Hamazon. WIth the definition given here that would be practically for every piece of cake or Boreka. So I prefer larger olives and eat a bit more Matzah at the seder...

    1. Bonkers. The minimum shiur for bentchsing on cake according to the strictest opinion is 3 eggs. That's at least 45 olives. In any case, the Gra holds that you don't bentsch unless you are koveia seudah. And furthermore washing your hands and bentshcing is fun unless for some reason you are saying a preposterously long nusah with a whole bunch of extra stuff at the end.

    2. It's not a "choice". It's what Hashem meant.

  4. Another problem is the inconsistency about size. Olives should be the same size regardless of the circumstances. If an olive is the size of a small Volkswagen for eating matzah it should be the same size for מאכלות אסורות.


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