The blessing on matza brei is mezonot, as long as the pieces of matza are smaller than 1.3 fl. oz. (39 ml, or 1/6 cup) each. If even one of the pieces is larger than 1.3 fl. oz., wash your hands and say ha'motzi before eating it.

To say any after-blessing/bracha achrona (al ha'michya, al ha'gafen, al ha'eitz, borei nefashot, or birkat ha'mazon), you must:

• Eat at least the minimum volume (1.3 fl. oz.--39 ml, or 1/6 cup) of solid food within four minutes, or
• Drink at least 3.3 fl. oz. (99 ml) of liquid within 30 seconds.

If Did Not Eat Minimum

Do not say bracha achrona if you did not eat 1.3 fl. oz. (39 ml) within four minutes.

If Did Not Drink Minimum

Do not say bracha achrona if you did not drink 3.3 fl. oz. (99 ml) of any potable liquid within 30 seconds. Note You may not combine the volume of solid food to liquid food or liquid food to solid food that you ate and drank in order to make the minimum volume for an after-blessing.

If Did Not Eat or Drink Minimum

Size: How To Calculate

Ounces: Weight or Volume

The minimum quantity for saying after-blessings is based on volume, not weight. If you eat a pack of pretzels whose volume is 1.3 fl. oz., even though the label says it only weighs 0.5 oz., you would say an after-blessing of al ha'michya.

Figuring Volume

Figuring Volume: Non-Mezonot Foods

You may not include the volume of fish or meat or other foods eaten together with bread or matza in order to reach a total volume of 1 fl. oz., which is required for saying the after-blessing of birkat ha'mazon. However, you may combine the volumes in order to say borei nefashot.

Figuring Volume: Unswallowed Pits/Seeds

When eating foods with seeds or pits (olives, pomegranates, etc.), do not include unswallowed seeds or pits to reach the 1.3 fl. oz. (39 ml, or 1/6 cup) minimum volume needed to say an after-blessing. You may include only what you have swallowed.

D'Oraita Cases

For d'oraita cases (halachot from the Torah), such as eating matza at seder or drinking wine for kiddush, we use a more stringent minimum measure:

• Eat at least 1.9 fl. oz. (56 ml) of solid food within four minutes, or
• Drink at least 4 fl. oz. (119 ml) of liquid within 30 seconds.

Timing

When To Start Counting

You may start counting the period of four minutes (for eating at least 1.3 fl. oz.) or 30 seconds (for drinking at least 3.3 fl. oz.) any time after the fore-blessing as long as it is continuous from when you first swallow until you have swallowed the minimum amount.

Three Shabbat Meals
We are required to eat three Shabbat meals, as a rabbinic (d'rabanan) enactment to enjoy Shabbat (oneg Shabbat). The first Shabbat meal must be at night and the remaining two must be during the day (the third meal must be eaten after halachic midday). Friday night dinner and the first meal on Saturday are preceded by kiddush. For the first two Shabbat meals, say ha'motzi over two complete loaves of bread, each of which is at least 1.3 fl. oz. in volume. For the third meal, the ideal is to use two complete loaves of bread, but the requirement of eating the third meal can also be fulfilled by eating any food other than salt or water.

Source of Saying Shabbat Kiddush

• Saying kiddush on Shabbat night is a commandment from the Torah (d'oraita).
• Saying kiddush on Saturday morning is a rabbinical (d'rabanan) enactment.

Note If you did not say Friday night kiddush, you must say that version of kiddush on Shabbat morning and it is then a requirement from the Torah (d'oraita). Do not begin with va'yechulu; instead, begin with borei pri ha'gafen and say the second blessing of kiddush.

Source of Kiddush Location
Saying kiddush at the place where you will eat your meal is a rabbinical (d'rabanan) enactment.

Shabbat Kiddush-Meal Quantities: Evening

• For evening kiddush, a minimum of 4 fl. oz. (119 ml) of wine must be blessed on and at least half must be drunk.
• For the evening meal, as on Shabbat lunch and all required Jewish festival meals, a minimum of 1.9 fl. oz. of bread must be eaten within four minutes.

Shabbat Kiddush-Meal Quantities: First Meal on Saturday
Shabbat day first meal has two separate eating requirements.  They may be combined (say/hear kiddush and start the main meal right away) but are often done separately (say/hear kiddush and then eat some mezonot; the main meal is eaten later in the day).
Note Since eating and drinking requirements on all morning kiddushes (both Shabbat and Jewish festivals) are d'rabanan, the required beverage amount for morning kiddush is only 3.3 fl. oz. (99 ml) instead of the d'oraita 4 fl. oz. (119 ml), which is required for kiddushes for Shabbat evening.
1) Morning kiddush requires a halachically legal “meal” with these elements:
      a) Blessing on a minimum of 3.3 fl. oz. (99 ml) of wine (or other beverage),
      b) Someone's drinking at least 2 fl. oz. of the beverage, followed by
      c) Eating at least 1.3 fl. oz. (39 ml, or 1/6 cup) of some type of mezonot (or bread) within four minutes.
Note If you drink at least 3.3 fl. oz. (99 ml) of wine within 30 seconds, you do not need to eat mezonot.
Note You do not need to drink the wine or other kiddush beverage to fulfill “establishing a meal.” You may hear kiddush and then simply eat the required amount of bread or mezonot. This applies to Shabbat or Jewish festivals, evening or morning.
The kiddush “meal” does not have to satiate.
Note If you have not fulfilled the requirements for kiddush, you may not eat other foods, such as fruit or fish at a kiddush.

2) The real meal (kovei'a se'uda) of Shabbat lunch requires eating at least 1.9 fl. oz. (56 ml) of bread (or matza during Passover!) within four minutes. It should include enough food to satiate.
Note You can simultaneously fulfill the requirement to “establish a meal” and to “eat a meal” by eating one (the same) piece of bread.
For details on fulfilling the first two meals' requirements, see Shabbat: Kiddush.

Shabbat: Eating a Meal Requirement: Third Meal
For details on fulfilling the third meal's requirements, see Shabbat: Third Meal (Se'uda Shlishit).