There is a lot of confusion as to what the proper equivalents of the measurements necessary to fulfill the obligations of the Seder. I’d like to briefly run through them here.
These are based on the “Laws of the Seder” by Rabbi David Feinstein Shlit”a.
The Four Cups
The volume needed for each cup used for the four cups is a revi’is. There are various ways of measuring this; for Biblically ordained Mitzvos we are stringent and require the volume of the cup to be 4.42 fluid ounces. For Rabbinically ordained Mitzvos it would be 2.9 fluid ounces.
One should preferably drink the entire cup, or at least the majority of it. If one has a lot of difficulty drinking wine he can drink as little as ¾ of an ounce, although it is preferable to drink at least a full ounce.
The wine should be drunk in under 2 minutes. At the very most it must be completed within 9 minutes.
One should use wine. The reason for this is that the Gemara specifically says it should have the ‘taste of wine’ which is understood by the Rishonim to mean intoxicating. Moreover, the wine symbolizes freedom which is obviously not fulfilled by non-alcoholic beverages.
Although wine and grape juice can be diluted at a ratio of 1:6 and still retain their halachic wine designation, the ‘demonstrating freedom’ concept discussed above would still be an issue if the wine is diluted to the point where it would have absolutely no intoxicating effect on the drinker. (This is obviously subjective). Additionally almost all wines are pre diluted and are already at least 20% water. Sweetened wines are further diluted, as are ‘light’ wines and grape juices. In fact Matzav.com reported that one should not further dilute Kedem light grape juice.
If one has difficulty drinking wine, they should use a small cup that holds just 2.9 ounces and drink a little more than half of it. If that is too difficult they should drink just 1 ounce or even a little less up to ¾ of an ounce. The least preferable option is to drink grape juice. Grape juice should be reserved for those whom wine would pose a health risk or would cause them to not be able to complete the Seder, even if they adhere to the above guidelines.
If no wine or grape juice is available at all, one may use ‘chamar medina’ which is something served to people as a token of honor, not just to quench their thirst. Thus tea and coffee would qualify. Rav Moshe Feinstein ruled that milk would as well, but not soda. (Other Poskim differ in this regard).
Karpas should be a green vegetable. If no greens are available any borei pri haadama may be used. (This may be why potatoes were used in Russia, but that reason is not applicable anymore and one should use a green vegetable now).
Additionally the vegetable should be raw. The reason for this is that Karpas is supposed to stimulate the appetite. The Gemara tells us that raw vegetables increase appetite, cooked ones satisfy it. (This would be another problem with potatoes).
It would seem logical that one should recline while eating Karpas but the standard practice seems not to recline.
One should dip before making the blessing.
The leader of the Seder must eat two Kezaysim, one from each of the two top Matzos. The other participants must eat one Kezayis and could be made up from other matzos if necessary.
You get two to nine minutes from the first swallow until you finish the full kezayas. It is best to fully masticate the first bite of Matzoh and then swallow so as to minimize the time of eating.
How much is a kezayis? The calculations vary from 0.7 fluid ounces to 1.5 fluid ounces. For the first nights first kezayis of Matzoh, which is Biblically mandated, one should have the larger amount – 1.5 fluid ounces. For the two kezayis rule, which is only a stringency, the smaller shiur would suffice, so 1.5 fluid ounces would suffice for that as well. This is equal to approximately 7 x 6.25 inches.
A kezayis of Maror is required. Since it is Rabbinic we can be lenient but one must have 1.1 fluid ounces of maror within 9 minutes. If one has a difficult time with this he can go down to 0.7 fluid ounces. The horseradish must be grated according to most opinions.
If using Romaine lettuce stalks one must use enough to cover an area of 3 x 5 inches. If using the leaves one must use enough to cover 8 x10 inches.
One must have a kezayis of Maror and a kezayis of Matzoh for the Korach sandwich.
One can be lenient about the shiurim – 7×4 inches for the Matzoh and 0.7 fl. ounces for grated horseradish. If one is using lettuce he should use the full amount. (because its easy).
One may rely on the lenient 9 minute time for completion of the Korach sandwich.
In order to meet the requirement of all authorities one should eat a 7×6.25 in. piece of matzoh for the Afikoman.