Required Amount of Matzah and Wine for the Seder
While it is a good idea to prepare in advance it is permitted to measure the matzah or wine on Pesach itself. Even though usually it is forbidden to measure on Yom Tov for the purpose of a mitzvah it is permitted.
The four cups of wine
How much the cup needs to hold
- The cup of wine must be filled with a Revi'it of wine and one must drink a full Revi'it or at least majority of a Reviyit. 
- If the cup holds more than a Revi'it, one can fulfill one's obligation by only drinking one Revi'it. However, because some hold that one should drink the entire cup, if one plans on only drinking a Revi'it one should use a cup that only holds a Revi'it. Additionally, if a cup holds a number of Revi'iyot, many people can drink from the same cup as long as there is a Revi'it for each person. 
- One should fill up the cup to the top even if it is large. 
How much must one drink
- Preferably, one should drink a Revi’it of wine for each of the 4 cups of wine at the Seder. If this is difficult, one fulfills his obligation by drinking the majority of a Revi’it for each cup. Some hold that one must have a majority of the cup. If one intends to drink the minimum amount one can be strict for this opinion by using a cup that is the size of a reviyit.
- The precise measurement of a Revi'it is a matter of dispute; several opinions are outlined below:
- Rabbi Mordechai Willig holds that a Revi’it is 2.5 fl oz (75cc). 
- Rav Ovadia Yosef writes that a Revi’it is 2.7 fl oz (81cc). 
- Rabbi Avraham Blumenkrantz writes that a Revi’it is 2.9 fl oz (86cc). 
- Rabbi Shimon Eider writes that according to his measurements, the Revi’it is 3.0 fl oz (89cc). 
- Rabbi Dovid Feinstein (Kol Dodi Haggadah, 5730, p. 4) writes that based on measuring large eggs, which should be used for the four cups, a Revi’it is 3.3 fl oz (98cc). 
- Rav Yisrael Belsky recommended having a Revi’it of 4.3 fl oz (127cc). 
- Rav Chaim Kanievsky writes that according to the rulings of the Chazon Ish, a Revi’it is 5.1 fl oz (150cc). 
- If a person is a diabetic and can’t have a lot of wine, the absolute minimum amount is 1.5 oz and a drop more and if one can’t have eat that much one doesn’t have to drink the wine. However, one should consult with one’s doctor who is Torah observant. 
Within what time should one drink the wine?
- It is preferable to drink majority of a Revi’it in one swallow. If one can't so, one should drink the wine within Kdei Sh’tiyat Revi’it. 
- After the fact, one must drink the cup within the time of a Kdei Achilat Pras (which there are opinions spanning from 2 minutes to 10 minutes) to fulfill the obligation, otherwise one must repeat drinking the wine. 
- Thus, one shouldn't take a cup that has a thin spout because one won't be able drink the whole cup at once. 
Types of wine
- There’s a positive mitzvah Deoritta to eat matza on the night of the 15th of Nissan. 
- There’s a mitzvah (which according to some is Deoritta) in eating more Matzah than the required amount. 
How much Matzah should one eat at the Seder?
- There's three times one should eat Matzah during the seder: Motzei Matzah, Korech, and Tzafun (Afikomen). To fulfill all of one’s obligations, one should eat 2 kezaytim for Motzi-Matza, 1 Kezayit for Korech, and 2 more kezaytim for Afikomen. All agree that having 2 kezaytim for Afikomen is merely preferable; one fulfills his obligation with 1 kezayit. 
- For Motzi-Matza, many authorities write that if the matzot of the head of the house don’t suffice for 2 kezaytim for each person, one fulfills his mitzvah by eating a bit from the whole matza and 1 other Kezayit (and not 2).
- Practically, how large in a Kezayit in terms of the amount of Matzah one should eat?
- According to Ashkenazim, for Motzei Matzah, some say that one should eat 4/5 of a machine matzah, some say 2/3 of a matzah, and others say 1 matzah. For Korech, some say that one should eat 2/5 of a matzah, some say less than 1/2 of a matzah, and others say 2/3 of a matzah. For Afikomen, some say that one should eat 4/5, some say more than 1/2, and others 1 matzah.
- According to Sephardim, some say that the Kezayit should be measured by the weight of 27 grams, and some say that it is measured by the volume and in weight the Kezayit comes out to be 20 grams. (The typical machine matzah is 30-32 grams. In general, the Kezayit can be calculated according to the weight printed on the box.)
Someone who is sick
- Someone who is sick and can’t eat so much Matzah can use the Kezayit evaluated according to a third of a KeBaytzah which according to Rav Chaim Noeh is 17.3 cc.  However, for a personal situation it would be advisable to consult one's Orthodox rabbi to determine the correct amount for one's individual situation.
Crumbs which were caught between one's teeth
- What stays between one’s teeth isn’t counted towards the Kezayit, however, that which is in one’s gums is counted towards the Kezayit. 
- Shulchan Aruch 306:7, Yechava Daat 1:16, Halichot Shlomo p. 209
- Shulchan Aruch 472:9. Rav Schachter at OU Pre-Pesach Webcast 5770 between minutes 93 and 94 says that people have the misconception that one only has to drink a sip of wine, however, in reality, one needs to have a Reviyit or at least a majority of a Reviyit.
- Beit Yosef 472:9 quotes the Kol Bo and Orchot Chaim, who say that if a cup holds many Reviyot, one still has to drink only a Revi’it. The Ramban, however, argues that one must drink majority of the cup even if it is larger than a Revi’it. Although S”A 472:9 rules like the Kol Bo, if one doesn’t plan on drinking a lot, Mishna Brurah 472:33 advises having a cup that holds only a Revi’it in order to satisfy the opinion of the Ramban.
- The Pri Chadash 472:9 writes that even if one has a cup bigger than a reviyit one should fill up the cup to the top because of hiddur mitzvah.
- * The Gemara (Pesachim 108b) states that each of the 4 cups at the seder must contain a Revi’it of wine. Additionally, Rabbi Yitzchak (Pesachim 109a) says that a certain measuring cup in Tzipori held the volume of a Log and they would use it to measure the Revi’it for Pesach. Rashbam (109a s.v. U’vah) explains that each of the 4 cups had to hold a Revi’it of a Log and altogether that would equal a Log, the exact volume of the cup in Tzipori. Rambam (Chametz UMatzah 7:7), Tur, and S”A 472:9 codify this as halacha.
- On the statement of Rav Nachman (Pesachim 108b) that one fulfills his obligation by drinking a majority of the cup, Tosfot (s.v. Ruba) comments that preferably, one should drink an entire Revi’it. The Bach (472 s.v. Mah SheKatav VeEin) writes that it is obvious that one should only rely on the concept of majority being considering like the entirety (Rubo K’kulo) after the fact, however, l’chatchila one should drink an entire Revi’it. Mishna Brurah 672:30 agrees.
- The Ramban (quoted by Orchot Chaim Leil Pesach no. 6, cited by Bet Yosef 472:9) holds that unlike a regular bracha made over a cup of wine which only requires majority of a reviyit the 4 cups of wine require a majority of the cup. Mishna Brurah 472:33 writes that the strict halacha follows the other rishonim.
- Mishna Brurah 472:33
- Background: The Gemara (Pesachim 109a) explains that a Revi’it is the volume of 2x2x2.7 fingerbreadths. Additionally, the Rashbam (109b s.v. DeHaynu) writes that the Revi’it is equal to 1.5 times the volume of an egg. Mishna Brurah 271:68 clarifies that the Revi'it is 1.5 eggs with its shell. Because of the apparent discrepancy between these two measurements, the Tzlach (Pesachim 116b) concluded that the egg of the days of the Gemara was twice the size of the modern-day egg. The Mishna Brurah 486:1 concludes that for the 4 cups of wine at the Seder, which are only d’rabanan, one need not follow the Tzlach’s strict view.
- Rabbi Mordechai Willig (“The Shiurim of Seder Night” min 1-10, and Pesach To-Go 5771 p. 60) holds that strictly speaking the size of an egg with its shell is 50 cc, and the Revi'it is 1.5 eggs with its shell, resulting in a Revi'it of 2.54 fl oz.
- Rav Ovadia Yosef (Chazon Ovadia p. 16) writes that the Revi'it is 81cc. This is based on the measurements of Rav Chaim Noeh (Shiurei Tzion p. 69) with slight adjustments.
- Rabbi Avraham Blumenkrantz (The Laws of Pesach 5771 pg 111) writes that since the four cups are Derabbanan one may use a cup that holds 2.9 oz.
- Halachos of Pesach (Rabbi Shimon Eider, Chapter 20, Sec D 5, pg 228-230) writes that since the four cups are Derabbanan one may have the smaller measurement which is measuring by eggs and not by thumbs and according to his calculation a Reviyit should be 3 oz and if one is unable to have a Reviyit one fulfills one's obligation with a majority of a Reviyit. See also Weekly Halacha (by Rabbi Neustadt on torah.org) who writes that one may rely on the view of Rav Chaim Noeh who holds that 3 oz is sufficient being that the cups of wine are Derabbanan.
- In the 5745 edition, however, he says that the Revi’it is 2.9 fl oz. See also Rabbi Yisroel Bodner (Halachos of K’zayis p. 24 n. 24) who writes that he spoke to Rav Dovid Feinstein about how he arrived at his measurements and was told that his father, Rav Moshe Feinstein, didn't measure it himself but rather a student measured 'large' eggs and came up with 2.2 fl oz per egg. Rav Dovid added, if he, Rav Bodner, arrived at a smaller measure with his own measurements he should follow that. Rav Bodner writes that according to his measurements the average egg was 55cc (1.92 fl oz). Nonetheless, in terms of Bracha Achrona Rav Bodner (p. 26) follows the measurements of Rav Chaim Noeh who measured the average egg to be 57cc.
- Rav Yisrael Belsky on OU Pre-Pesach Webcast 5771 between minutes 37 and 38
- Shiurin Shel Torah p. 65. See also Halachos of Pesach (pg 229) who writes that the Kiddish cup of Rav Yisrael Salanter was 4.1 oz at it's full capacity and the cup of the Chafetz Chaim was 5 oz.
- Rav Yisrael Belsky on OU Pre-Pesach Webcast 5771 between minutes 51 and 52:30
- Magen Avraham 472:11 writes that one should drink the wine within Kdei Sh’tiyat Revi’it and after the fact within Kdei Achilat Pras. He adds that it's preferable to drink the majority of a Revi’it in one swallow. Mishna Brurah 472:34 agrees. Although the Machatzit HaShekel 472:11 extends this to drinking the entire cup in one drinking according to those who say one should drink the entire cup, Rabbi Dovid Feinstein (Kol Dodi Haggadah, 5730, p. 4) argues that it is impossible for a person to swallow that much wine at once.
- Rama 472:9 in name of the Roke'ach quoted by the Bet Yosef writes that one shouldn't drink with a large pause. Magen Avraham 472:11 explains that the long pause is a Kdei Achilat Pras. Mishna Brurah 472:34 rules like the Magen Avraham and adds that even though the Ashkenazi practice is not to repeat to drink the third and fourth cup if one forgot to lean because it may look like one is adding a cup to the established cups, even so here one should repeat because one has not fulfilled his obligation according to anyone.
- Rama 429:15
- Rambam (Sefer HaMitzot #158) writes that eating matzah nowadays is a Mitzah Deoritta. See Chatom Sofer (CM 196 Hashmatot) who points out that Matzah is the only Biblical mitzvah we have nowadays.
- Maharal in Gevurot Hashem chapter 48, Bach 472, Mikrei Kodesh siman 48, Sh”t Har Tzvi 2, and Natai Gavriel (vol 2, 90:26) hold that there’s a mitzvah of eating Matzah as much as one eats even beyond the actual requirement. See also the Emek Shelah (Yitro 53:4). Hagadat Be’er Miryam (pg 53) writes that another reason to eat more Matzah is because there’s a big confusion in the amount necessary and Matzah is a mitzvah Deoritta. Rav Mordechai Willig (Pesach To-Go, Nisan 5771, p. 60) quotes Rav Soloveitchik who derived this insight from the Rambam Chametz UMatzah 6:1.
- It is clear from the Gemara (Brachot 37b, Pesachim 108a and 119b) that one fulfills his obligation of eating matza with one kezayit. Rambam Chametz UMatzah 6:1 and Ritva Pesachim 35a write this explicitly. Nonetheless, the Rosh Pesachim 10:30 writes that one should eat a Kezayit of the whole matza and a Kezayit of the broken one. This Rosh is codified by the Tur and S”A 475:1.
- Many achronim wonder where the Rosh found a source for requiring two kezaytim. Bach 475:3 suggests that the Rosh was strict for the opinion that one needs to eat a Kezayit each time one makes HaMotzi (a minority opinion rejected in S”A 210:1). The Prisha 475:2 explains that the Rosh meant since there is a dispute in the Rishonim whether the Al Achilat Matza should be made on the broken one (Rashi Pesachim 116a) or the whole matza (Hahagot Maimon (Seder #7)), one should have a Kezayit from both. This sentiment is echoed by the Taz 475:2 and Mishna Brurah 475:9.
- Despite the questions of the achronim, the Rosh’s view is accepted by most acharonim, including Magen Avraham 475:4, S”A HaRav (Piskei HaSeder), Kitzur S”A 199:5, Aruch HaShulchan 475:5, and Chazon Ovadyah (p. 65). See, however, Orchot Rabbenu (vol 2, p. 70) who writes that Chazon Ish personally ate only one Kezayit because he held the halacha doesn’t follow the Rosh.
- For Korech, Mishna Brurah 475:16 writes that a Kezayit of matza is needed. Kitzur S”A 199:7, Nitei Gavriel 59:1, and Chazon Ovadyah (p. 100) agree.
- Regarding Afikomen, S”A 477:1 rules that one should eat one Kezayit of matza. Darkei Moshe 477:2 quotes the Maharil that it is preferable to have 2 kezaytim. Magen Avraham 477:1 explains that one is in commemoration of the Korban Pesach and one for the matza eaten with it. Many achronim quote the Maharil including the Taz 477:1, Kitzur S”A 119:8, Mishna Brurah 477:1, Kaf HaChaim 477:1, and Chazon Ovadyah (p. 106).
- Rav Shlomo Zalman in Halichot Shlomo 9:40 rules that if the head of the house’s three matzot do not suffice for the Kezayit for each person, each person should just have a piece from the whole matza and eat a single Kezayit of matza from other shemura matza. He explains that according to the Prisha, if one isn’t eating from the head of house’s matzot, there’s no safek upon which matza one makes Al Achilat Matza, so there is no need to eat an extra kezayit. Chazon Ovadyah (p. 65), Haggadah Moadim UZmanim (p. 97), and Seder HaAruch (p 455) quoting Rav Elyashiv agree. Rav Dovid Feinstein in Haggadah Kol Dodi (5745 edition, 14:3) says the same idea. See, however, also Sh"t Igrot Moshe OC 5:16 who thinks that one should avoid this situation by everyone having their three matzot. On that last point, see the full discussion here.
- Mishna Brurah 486:1 writes that Tosfot holds a Kezayit is half of a KeBeitzah with the shell and the Rambam holds it is a third of a KeBeitzah (see Tosfot (Yoma 80b s.v. Agav), Rambam (Eiruvin 1:9)). Rav Avraham Chaim Noeh (Shiurei Torah 3:12) argues that Tosfot holds half a KeBeitzah without the shell. Mishna Brurah 486:1 rules that for Deoritta Mitzvot and Bracha Achrona, one should eat the size of half a KeBeitzah, but for Derabbanan Mitzvot, one third suffices. He adds that since one has to make a Bracha on maror, one should eat half a KeBeitzah.
- The Tzlach (Pesachim 116) holds that the modern day eggs are half the size of those in the days of Chazal. However, Rav Noeh (Shiurei Torah Shaar 3) argues that the modern day eggs have not changed from the days of Chazal. Mishna Brurah 486:1 writes that for the mitzvah deoraitta of matza, one should follow the stringent view of the Tzlach. Even though Vezot HaBracha (pg 6, Birur 1, pg 221) quotes Rav Elyashiv and Rav Shlomo Zalman saying that for Bracha Achrona the widely accepted measurement of the Kezayit is according to Rav Chaim Noeh, in regards to the mitzvah of eating matza, Rav Shlomo Zalman writes in Halichot Shlomo 9:13 that one should be strict for the size of the Kezayit of the Chazon Ish which are based on the opinion of the Tzalach.
- Practically, how much matza is that? The following measurements are in regards to a piece of the average machine matza. Rabbi Dovid Feinstein (Haggadah Kol Dodi, 5745 p. 1) notes that matzah which fills the volume of 1.5 fluid ounces (44cc) weighs 31 grams (coming out to 705kg/m^3 which is about 70% the density of fresh water).
- (1) Halachos of Pesach (p. 242) quotes Haggadat Kol Dodi (Rav Dovid Feinstein) that for Motzi-Matza, one should eat 6.25”x7” (about one matzah), for Korech 4”x7” (about 2/3 of a matza) and for Afikomen 6.25”x7” (about one matza).
- (2) Rabbi Bodner in Halachos of K’zayis (p. 93) quotes Rav Moshe Feinstein saying that 43.5cc (about 2/3 of a matza) is sufficient for both kezaytim of Motzi-Matza. Rav Yisrael Belsky on OU Pre-Pesach Webcast 5771 between minutes 30:30 and 37 endorsed this opinion. He added that if one is able, it's preferable to have the larger amount similar to the Chazon Ish's Kezayit. [Rabbi Bonder (pg 92-95) explains that if one is using hand made matzah it depends on how thick the matzah if which can be determined by seeing how many matzah are in a pound. If there's 9 to a pound, it's thin, 7.5 to a pound medium, and 6 to a pound thick. For Motzei Matzah, if it's thin, use slightly more than half, if it's medium, use slightly more than two fifths, if it's thick, a little more than a third. For Korech, if it's thin, use less than a third, if it's medium use a quarter, and if it's thick use a fifth. For Afikomen, if it's thin, use two fifths, if it's medium use less than a third, if it's thick use slightly more than a quarter.]
- (3) Rav Mordechai Willig (Pesach To-Go, Nisan 5771, p. 60) rules that a Kezayit is 22.5cc (less than 2/5 of a Matza). See also Am Mordechai Moadim (p. 152).
- (4) Rav Chaim Kanievsky in Shiurin Shel Torah (p. 66, 5750) writes that for the first Kezayit one should have 2/3 of a matza. (This is a retraction from what he wrote in Shiurin Shel Torah (p. 87, 5716) that a half of a matza is a kezayit).
- Kaf HaChaim 168:46 quotes a number of Sephardi Achronim, including the Chida, who say that the minhag of Sephardim is to measure the Kezayit by weight. He writes that this is the common minhag even for measuring a Kezayit of matza. Rav Ovadyah in Yechave Daat 1:16, Rav Mordechai Eliyahu (Maamar Mordechai 11:96), and Rav Chaim Dovid HaLevi (Aseh Lecha Rav 6:45) agree. Yalkut Yosef 475:4, therefore, rules that a Kezayit of matza is 27 grams. [In general, one machine matza is between 30 and 32 grams and so a Kezayit is .85-.9 of a matza.]
- However, Rav Ben Tzion Abba Shaul (Or Letzion vol 3, p 30) argues that the minhag only developed when matza had a similar density to water, but because our matza is thin and dry, there is no need to be stringent to calculate based on weight. Accordingly, he calculated a Kezayit to be 29cc, which he says is less than 20 grams in weight.
- Mishna Brurah 486:1, Halichot Shlomo (pg 214 note 55)
- This is simply good advice so that the Rabbi is able to consider the situation and apply the appropriate leniencies one's individual situation.
- Piskei Teshuvot 486:1, Natai Gavriel (vol 2, 91:7)