3,634. How Much is an Omer?

Hilchos Bikkurim 6:15

The smallest volume of dough from which challah must be taken is a whole omer of flour. This is so regardless of whether it was made from one of the five species of grain or from a mixture of all five because they combine to form the minimum volume. An omer is one-fifth of a kav less than two kav. [In practical terms, 3 lbs. 11 oz. is the accepted standard.] A kav is four log and a log is four reviis. A reviis is the volume of a cube two fingerbreadths by two fingerbreadths by 2.7 fingerbreadths. A fingerbreadth is the width of a thumb. The result is that an omer is ten fingerbreadths by ten fingerbreadths by about 3.9 fingerbreadths. A cube whose sides are 6.78 fingerbreadths equals the volume of an omer. An omer equals 43.5 eggs, which is the same as 86.67 sela of Egyptian wheat flour. The Rambam says that’s 520 Egyptian zuz in his day. A volume that contains that weight of wheat is universally accepted as the measure that needs challah taken.

For further assistance, please consult the Guide to Halachic Measures.

Hilchos Bikkurim 6:16

One may not make his dough smaller than the minimum volume in order to avoid taking challah. If someone takes challah from a dough that is smaller than the minimum volume, he has accomplished nothing; it remains regular dough. Let’s say that someone makes dough smaller than the volume that requires challah to be taken. He bakes it, put it in a basket, and then bakes another such loaf. He puts that in the basket and continue in this manner until the basket contains a volume from which challah must be taken. In such a case, the basket combines the loaves, obligating them in challah, so he must take challah from the bread. This is learned from the Numbers 15:19: “When you eat the bread of the land.” We see that one must take challah even from bread that was baked. However, an oven doesn’t combine loaves in order to obligate them in challah.