How Much is a Shiur?

On pesach it is necessary to know how much matzoh is needed for a kzayis, in order to perform the mitzvah of matzoh. To comply with this requirement, Hagaon Rav Moshe Feinstein zt\”l ruled to use an amount of matzoh which will displace 1 ½ fl. Oz., (an amount equal to 2/3 of a standard machine matzoh). If one wishes to conform to the most stringent interpretation of the ruling of the Chazon Ish zt”l he should use a slightly larger shiur, 1.69 fl. Oz (an amount equal to slightly more than 2/3 of a standard machine matzoh).
Handmade matzohs (commonly referred to as shmurah matzohs), can vary significantly in weight, size and thickness and from one matzoh to another. For this reason, it is impossible to assign a precise shiur as a standard kizayis for all hand matzohs.
One can, however, get a close approximation of the shiur needed, by first seeing how many matzohs he has per pound. Typically thin matzohs come 9 matzohs to a pound, medium matzohs come 7 to a pound, and thick matzohs come 6 to a pound. He can then use the following guidelines:
If he has thin matzoh – he should use slightly more than one half of a matzoh
If he has medium matzoh – he will need more than a third and less than a half of a matzoh.
If he has a thick matzoh – he should take a little more than one third of a matzoh.

Pesach – Passover
Kïzayis – Size of an olive (volume approx. one fluid oz., 28.8 cubic centimeters)
Mitzvah – Torah or Rabbinic commandments
Shiur – Amount

Reprinted from Halachos of Kizayis by Rabbi Pinchos Bodner with permission of Feldheim Publishers

Thin Matzoh
Medium Matzoh
Thick Matzoh