"And you shall count for yourselves from the day following the Shabbat,1 from the day that the Omer that was waved was brought. They shall be seven complete weeks." (Leviticus 23:15-16)

What’s the Mitzvah?

The Torah tells us to count 49 days (seven weeks) starting from the day the Omer offering was presented in the Temple (the second day of Passover) and then celebrate the holiday of Shavuot on the 50th day.

Read: 13 Facts About Counting the Omer

How to Count?

Before counting the Omer, the following blessing is recited:

Blessed are You, L‑rd our G‑d, King of the universe, who has sanctified us with His commandments, and commanded us concerning the counting of the Omer.

Counting Days and Weeks

The Torah tells us to count both 50 days2 and 7 weeks,3 so we do both. For example, on the 16th day, we’d say: “Today is 16 days, which is two weeks and two days of the Omer.”

What happens if you just counted the days? That would be acceptable and you would not need to count it again—except on days when the count is divisible by seven, when a week is completed. On those days, if you neglected to tally the week, you should count again without a blessing.

What if you just counted the weeks? Then you didn’t do the mitzvah and should recite the blessing and count properly.4

Standing

We stand when making the blessing and counting the Omer. If you’re not able to stand or already counted while sitting, you still fulfilled the mitzvah, since the Torah doesn’t explicitly require standing for this mitzvah.5

See Why Count the Omer Standing Up?

When to Count?

Ideally, the counting of the Omer should be done each evening after nightfall (tzet hakochavim), when the new day has begun on the Jewish calendar. However, if you counted any time after sunset, you’ve fulfilled the mitzvah.6

You can count the Omer up until dawn, but the best time to do it is at the start of the night, after evening services (Maariv).7

Suppose you pray in a congregation that completes Maariv after sunset (as can be done under certain conditions and is quite common in certain locales) but would like to count after nightfall. In that case, you should count with the congregation without reciting a blessing and mentally stipulate:

"If I don't remember to count with a blessing later, let this counting fulfill my obligation. However, if I do remember later, I intend not to fulfill my obligation with this earlier counting."

Then, when you do remember later after nightfall, you should count again with a blessing.8

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Who Should Count?

As with many time-bound mitzvahs, only men are obligated to count the Omer. Nevertheless, many women have “accepted upon themselves” to do it as well. There are different opinions as to whether women should recite the blessing before counting9; Chabad women are among those who do say the blessing.10

Read: Why Are Women Exempt From Many Time-Bound Obligations?

Although not technically obligated, many children also count the Omer, eagerly looking forward to the holiday of Shavuot.

Read: When Do Children Start Doing Mitzvahs?

Eating Before Counting

As a general rule, when we have an important time-related mitzvah to do, we don’t eat, lest we get carried away with our eating and neglect the mitzvah.

So for a half hour before the time for counting the Omer (sunset), we don’t eat a meal that contains bread (this applies even if you’ve already prayed Maariv but haven’t yet counted the Omer).11

However, if you set an alarm, are particular to always attend services, or appoint someone to remind you, you can eat, since you most likely won’t forget to count.

What if you started a meal without putting any safeguards in place? If you began the meal before nightfall, you can continue eating and count when you’re done. However, if you began eating once night had already fallen, you need to pause, count, and continue eating.12

Note that the above only applies to meals that include bread. You may, however, snack before counting the Omer.

What If I Forgot to Count?

I Forgot Until the Morning: If you did not count all night and remembered the next day, count when you remember without saying the blessing. When you count the following days, you may do so with a blessing as usual.13

I Missed an Entire Day: If you forget to count the Omer for an entire day, meaning you missed counting both at night and the following day, you should continue counting on the following nights without reciting a blessing (it makes no difference what day of the Omer was missed).14

In this case (and in any instance when you do not say the blessing), you still say the other prayers traditionally said together with the Omer count.

When in Doubt: If you’re unsure whether you missed a day, you may count with a blessing on the subsequent days.

The same would apply if you messed up a previous count and should have counted again (without a blessing) but neglected to do so.

Why is this?

As a general rule, when there is a doubt about whether you’re obligated to do a mitzvah, you don’t say the accompanying blessing, since you don’t want to evoke G‑d’s name in vain.15

In this case, however, there are two layers of doubt:

  • Perhaps you actually did count.
  • Perhaps the halachah follows those who rule that each day is independent, so missing a previous day has no bearing on today’s obligation.16

Read: What You Need to Know About Saying a Blessing in Vain

Oops! Did I Just Accidentally Count?

If the time for counting has arrived but you have not yet officially counted and you casually mention the count of that night, you should formally count again, but without a blessing, since you may have just done the mitzvah.

For example, if someone asks you, “What night do we count tonight?” and you respond, “Today is 19,” it’s as if you did the mitzvah and you’ll have to count that night without the blessing.

This applies regardless of the language used and whether you mentioned just the days or also the weeks.17 Counting the weeks alone, however, is of no consequence. Even if it's the end of a week (e.g., day 7, 14, etc.) and you only mention the weeks, you should repeat the count with a blessing.18

If you simply said the number of days without specifying “today is,” then you definitely didn’t do the mitzvah and should count as usual.19

Lag BaOmer: Perhaps the day of the Omer when there is the most potential for this to be an issue is the 33rd day of the Omer, the festive day known as Lag BaOmer (“Lag” is shorthand for “33”). You may be tempted to say “Tonight is Lag BaOmer” before you count the Omer. If you do accidentally say this, there are differences of opinion as to whether you would count again with the blessing, since saying “lag” doesn’t fulfill the obligation of counting the Omer.20

Happy counting!