The Proper Amount for Washing Before Meals and After Eating

Hello

The halacha is as follows: For a kezayit of bread, one washes hands without a blessing and recites Hamotzi before eating, and Birkat Hamazon afterward as usual [though the blessing in this case is rabbinic]. For a quantity the size of an egg, one washes hands with a blessing and recites Hamotzi before eating, and Birkat Hamazon afterward constitutes a biblical requirement.

For less than a kezayit, one does not need to wash hands according to the letter of the law [though it is advisable to be stringent and wash without a blessing]. One recites the Hamotzi even on this, but does not say Birkat Hamazon for less than a kezayit.

The measure of a kezayit of bread: Some say it corresponds to the volume of an olive today, which is approximately 3 cm³, while others increase the measure up to 27 cm³!!! Thus, one should not eat without the final blessing for more than 3 cm³ and should not recite the final blessing for less than 27 cm³ in order to avoid doubt. For example: A slice of bread from the middle of a regular sliced loaf is about 125 cm³!!! Therefore, a quarter of a slice already contains the measure of a kezayit.

The measure the size of an egg for washing hands with a blessing is: 54 cm³ according to those who minimize, and 100 cm³ according to those who maximize, so one who wants to wash hands with a blessing and remove doubts should ensure to eat about 100 cm³.

In everything written thus far, we consider only the bread that one consumes throughout the meal. One must eat the quantity the size of an egg at once and not in separate portions in order to bless on the washing without interruptions.

Good luck - Menashe Israel