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The Magic Omer Formula: How to Figure Out the Correct Count without A Calendar or Internet!

04/22/2015 02:22:22 PM


By Shamai Leibowitz

If you were stranded on an island without a Jewish calendar and no internet connection (oy gevalt!), how would you know what number to count in the Omer?

Every year, on the second night of Passover, we begin a special 49-day period in the Jewish calendar known as Sefirat Ha’omer, the counting of the Omer.

Counting the Omer is a Biblical mitzvah, mentioned in Leviticus 23:15, and it is performed consecutively for 49 nights by reciting a blessing followed by the correct count of that particular night. On the first night – “Today is one day to the Omer”, on the second night – “Today is two days to the Omer” and so on, until the 49th night – which is always the night before Shavuot.

Rabbi Soloveitchik interprets this mitzvah as a sign that we control our own time – which is the mark of free people, while other commentators offer interesting and profound explanations for this mitzvah. The problem, however, is how to remember the correct count for any particular night, especially now that we’re past the first week. This Friday, for example, is it 14 or 15 or 16 to the Omer?

Sure, you can look up a Jewish calendar or go online and find websites, but what if you don’t have access to calendars or to the web? Imagine you are in an army operation where no electronics are allowed? Or what if you’re hiking on the Appalachian Trail?

Magic Formula: G.S.S–7

Every year there is a magic formula to figure out the correct Omer count on any given night. It can be summarized with the acronym G.S.S – 7 which means:

  1. GUESS a number
  2. SUBTRACT the day of the week (Sunday=1, Monday=2, etc).
  3. SUBTRACT magic number 1
  4. If your result is DIVISIBLE BY 7 (or it’s 0), your guess is right. If not – make another guess and repeat the process.


Let’s see how this formula saves the day by following the story of the Amars who went on a vacation to the Pago Pago Islands.

Yaakov and Rachel Amar felt they needed quality time together, so they left all their smartphones and tablets back home, and traveled to the romantic Pago Pago Islands. They arrived there on Friday April 24, and immediately relished the amazing landscape and inviting beaches of these American Samoa islands.

On Friday night, as they were about to begin a Shabbos meal, the Amars remembered that they haven’t counted the Omer. Just as they were about to begin the blessing, they realized, to their chagrin, that they forgot what’s the correct count! Because they were so excited about the trip – they couldn't remember what’s the Omer count tonight. They had no calendar, and it's Shabbos (so they couldn't call anyone), and anyway, there is no wireless service on this island. 

Both of them knew the Halakhic rule that if you forget to count one night, it irreparably disrupts the count, and you are not allowed to continue counting the Omer with a blessing on any of the following nights. The Amars became crestfallen, deeply concerned because they were about to lose the privilege to perform this special mitzvah. An otherwise magical vacation was about to be ruined. 

Just when they thought all is lost, Rachel remembered the magic formula. Excitedly, she exclaimed: “Guess, subtract day, subtract magic number 1, divisible by 7?”

She proceeded to make a reasonable guess. “Let’s try 22 for tonight’s Omer number. After all, we started counting about 3 weeks ago so it must be in this range.”
Applying the formula, from her guess of 22 she subtracted the day of the week, Friday:

22 – 6 = 16

She then subtracted magic number 1:

16 – 1 = 15

The result, 15, is not divisible by 7. That means her original guess (22) is wrong. 

Catching on quickly, Yaakov realized they need to refine their original guess so he suggested “Let’s try 21 and see what happens.”

They reapplied the magic formula:

21 – 6 – 1 = 14


The result, 14, is divisible by 7, showing that the refined guess of Omer count 21 is the correct count for this Friday night!

They did it! Without any connection to the outside world, our couple figured out that this Friday night, April 24, we count 21 in the Omer.

They high-fived each other, drank a L’chayim, and made the blessing over the Omer, joyous that they were able to perform this mitzvah and count the Omer properly.

This formula will work for any night of the Omer this year, with a small caveat that your guess has to be within a range of 7 of the correct count. That should not be a problem because most people know the approximate range we’re in so their guess is not completely wild.

The formula is good for every year, but the magic number changes. You'll need to come back to our website to get next year's magic number. But for the current Omer season, this formula will ensure that even if you find yourself on the amazing Pago Pago Islands or simply got stuck without your smartphone, you’ll never forget the correct Omer count. 

Wed, August 10 2022 13 Av 5782