What is the minimun size Kiddush cup that one can use for Shabos Kiddush?
Answer:
The minimum size for a kiddush cup is 86cc (2.91 fl oz). For Friday Night kiddush, some poskim write that one should use the larger cup of 150cc (5.07 fl oz), which is the Chazon Ish shiur (Biur Halachah to 271:13 writes that for Torah mitzvos one should use the larger shiur, and adds that although kiddush on a cup is not a Torah mitzvah, because the actual kiddush is de’oraisa, it is proper to use the larger shiur, or at least two kebeitzim, which works out to 115 cc or 3.9 fl oz). Others rely on the smaller shiur even for the Friday Night kiddush, citing proofs that this is the ‘true shiur,’ and that this is the custom.
