- Peninei Halakha
Based on the well-known rule that women are exempt from positive time-bound mitzvot, women are exempt from the mitzva of sefirat ha-omer, as it is dependent on time (see Peninei Halakha: Women’s Prayer, ch. 3, for the reason for this rule).
However, a woman who wants to perform this mitzva may do so, and she is credited for doing the mitzva. We likewise find that women customarily hear the shofar on Rosh Ha-shana and shake a lulav and sitting in the sukka on Sukkot.
However, the poskim debate the issue of the berakha. According to Shulĥan Arukh (589:6), women do not recite berakhot over such mitzvot, and this is the prevalent custom among most Sephardic women. The Ashkenazic custom follows Rema, who maintains that women who perform time-bound mitzvot may recite the berakha (see Peninei Halakha: Women’s Prayer 2:8). However, some Ashkenazic poskim rule that women should not recite a berakha when they count the omer because they do not pray Ma’ariv in the synagogue and are therefore more likely to miss a day. As we learned above, one who forgets to count a day may not continue counting with a berakha, and perhaps a particular woman will not realize that she forgot to count and will continue counting with a berakha (mb 489:3). Others say that women should not count the omer for kabbalistic reasons (Rav Pe’alim vol. 1, Sod Yesharim §12). On the other hand, still others claim that the Ashkenazic custom is for women to count (ma 489:1).
Therefore, a woman who knows that she can successfully complete the entire count, and knows to continue counting without a berakha even if she misses a day, may count with a berakha according to Ashkenazic practice. This is especially true for a woman who prays Ma’ariv every evening or whose family members are in the habit of reminding her to count. According to Ashkenazic custom, she may count with a berakha if she desires, because the chances that she will forget to count are relatively slim.