The squareness of the Tefillin: The requirement areas, measurement, and cases of damage

The squareness of the Tefillin:[1]

It is a Halacha from Moshe on Sinai that the Tefillin must be square. This applies to both the head and arm Tefillin. Thus, if the Tefillin is not square, it is invalid.[2] [Nonetheless, there is discussion amongst the Poskim as to the exact definition of a square and as to what parts of the Tefillin it applies to. The following is the final ruling of Admur on the subject, with other opinions noted in the footnotes.]

The squareness by the Shel Rosh:[3] By the Shel Rosh, all the four Batim together are to form a square, and not each Bayis individually. Nonetheless, initially, one is to form each of the four Batim to have the same dimensions, that one should not be wider than another.[4]

Definition of square:[5] The square must be exact, that its length is equal to its width [i.e. not a rectangle] in a way that its diagonal from one corner to the opposite corner is approximately[6] 2/5th larger than the length [not rhombus]. [For example, if the length is 50 centimeters, then the diagonal is to be approximately 70 centimeters.]    

The areas that must be square:[7] The Tefillin must be an exact square in all of the following areas: 1) The bottom area which is called the Titura.[8] 2) The sewing must be an exact square, which means that the length of the sewing must be equal to the width of the sewing.[9] 3) The actual Bayis must be square, which means that the length of the Bayis must be equal to the width of the Bayis.[10] (It must be square throughout its entire height.[11]) However, its height is not required to be equal to its length and width, and hence the Bayis remain Kosher even if its height is greater than its length and width.[12] If any of these areas are not square, the Tefillin is invalid.[13]

If the square became damaged with time:[14] If the required area was properly square, and after some time the square became damaged in one of the above required areas, it must be fixed. The Tefillin is invalid until it is fixed.[15]



It is a Halacha Moshe Misinai that the Batim must be square.

In what areas must the Tefillin be square? The Tefillin must be square by the Bayis [top], and the entire Titura, which includes the bottom and top. [In total, all 12 corners must be square.] The Maabarta does not have to be square and therefore even it became banged up, it remains Kosher.



Bedieved, may one nevertheless wear the Tefillin if they are not square?

If the Tefillin are not square in any of the areas mentioned above, then they are invalid, as stated above, and hence there is no use in putting them on even if no other Tefillin are available. Nevertheless, some Poskim[16] rule that if no other Tefillin are available then they are to be worn without a blessing. This especially applies if only the Bayis has lost its squareness, while the sewing has retained its squareness.[17]


How exact must the square be?[18]

Practically, the Torah was not given to angels and hence so long as it appears like a perfect square to the naked eye, as opposed to another shape [rectangle, parallelogram; trapezoid; etc], then it is considered valid. This applies even if under measurement of a rule, the dimensions are not exactly equal.[19] Nonetheless, today the custom amongst all Batim Machers is to make it an exact square.


How often must one verify the squareness?[20]

One is not required to measure it daily, and rather it retains its Chazaka unless one sees that its square has become damaged.


Q&A on what areas must be square

Must the Bayis rest in a symmetric square position on the Titura, with an equal distance from all sides?[21]

Yes. If it rests in a diagonal, or is recognizably closer to one side of the Titura, then it is invalid.


Must both the top and bottom area of the Titura be square?[22]

Both the top and bottom area of the Titura must be a square.


Must the Mabarta be square?[23]

No. For this reason, it is customary to make a cut between the Mabarta and Titura to emphasize the squareness of the Titura.


Must the square sewing on the bottom of the Titura be parallel to the square of the Bayis?

Some Poskim[24] rule that the sewed square must be parallel to the square of the Bayis, otherwise the Tefillin is invalid.


Must both the top and bottom area of the sewing be square?[25]

Both the top and bottom area of the sewing must be a square.


Q&A on a damaged Bayis

If the side of the Bayis or Titura has become “swollen” [i.e. protrudes] or has partially become dented in, is it Kosher?[26]

It is to be fixed.


If the four Batim of the Shel Rosh began to come apart is the Tefillin valid?[27]

If the squareness of the Bayis has been lost due to the compartments spreading apart, then some Poskim[28] rule that so long as the compartments can be squeezed together to form back the square then the Tefillin remains valid. Other Poskim[29], however, rule that so long as the Bayis no longer looks square, it is invalid. If, however, the amount of air between the compartments does not ruing its squareness, then it remains Kosher.


If the Titura began to split and come apart is the Tefillin valid?[30]

If the Tefillin has cracks by its bottom, as is common to occur between the lower and higher Titurah which have been sewed, it remains Kosher so long as the stitches have not been torn and the Titura maintains its square shape.[31]


What is the law if there is a hole in the side Titurah area of the Tefillin?[32]

So long as the hole does not affect the top square of the Titurah it remains Kosher, even if it is a large hole.


May dents or holes in the Bayis or Titura be filled with glue to complete its square state?[33]

This is not to be done even to the Titura, and certainly not to the Bayis.


If a chip or dent occurred on the Bayis or Titura, is it invalid?[34]

So long as the Tefillin retains its square shape to the naked eye, it remains Kosher. Nevertheless, if the dent/chipped area is the size of “Chagiras Hatziporen” [that a hand nail would get stuck in it, which is approximately a depth of 1 millimeter], then it is to be fixed. This especially applies by the corners of the Bayis.


If the top corners of the Bayis/titura became rounded, is it Kosher?[35]

If the top corners look rounded it is to be fixed.


If the sewing on the bottom of the Tefillin lost its square shape is it valid?

If the sewing on the bottom of the Tefillin lost its square shape, then it is invalid and new Batim are to be purchased. However, this only applies if its loss of a square is apparent to the naked eye. If, however it attains a square shape to one’s eye, but under close measurement is seen to be slightly uneven, then it remains Kosher. Practically, the accepted ruling is to allow for up to a 1-millimeter difference. This commonly occurs due to putting on Tefillin with wet or sweaty hair, and is hence to be avoided.



Verifying the Kashrus of the squareness of the sewing of your Batim:[36]

It occurs at times that the squareness of the Tefillin becomes damaged due to contact with a hard object, and other forms of impact. While this damage can certainly affect the Kashrus status of the Tefillin [depending on the level of damage done], there is a much more prevalent “squareness destroyer” which can deem the Tefillin invalid which takes place right under the Tefillin, and that is moisture and sweat. Moisture of one’s hair, whether due to sweat or showering, penetrates the Tefillin’s leather and with time begins to expand it. Eventually this can cause the squareness of the sewn area on the bottom of the Tefillin to lose shape and become invalid. While many are aware of the requirement for the actual Bayis to be square, many are unaware of the requirement for the sewed areas to also be square, and if this squareness is damaged, the Tefillin are invalid. Thus, one is to be very careful not to wear Tefillin with wet hair, at least not on a consistent basis, and one should also periodically look at the bottom of his Tefillin to verify that the sewing’s squareness has not been altered. One who sweats a lot on his way to Shul should preferably use a towel to dry his hair prior to putting on his Tefillin. If one sees any alteration that has taken place, it is to be brought to a Rav who is expert in Stam for checking.


[1] Admur 32:59; Michaber 32:39; Mordechai Hilchos Tefillin; Rambam Tefillin 3:1; Braisa Menachos 35a; See Biur Halacha 32:39 “Sheyiyu”; Piskeiy Teshuvos 32:60 in footnotes; 62-64

[2] Admur ibid; Rambam Tefillin 3, brought in M”B 32:173

Other opinions: Some Poskim rule that if the Tefillin are not square they nevertheless sremain Kosher. [See Biur Halacha 32:39 “Sheyiyu” in name of Rashi]

[3] Admur ibid; Rama ibid; Baruch Sheamar 109; Sefer Hateruma 209

[4] The reason: This is required as a Mitzvah due to Noiy Tefillin. [Olas Tamid 32:50; Kol Yaakov 32:182]

[5] Admur ibid; Michaber ibid; Rav Papa in Menachos ibid

[6] Admur ibid; M”A 32:53

[7] Admur ibid; Michaber ibid; Keses Hasofer 32:21

[8] Admur ibid; Michaber ibid; Sefer Hateruma 209

[9] Admur ibid; Michaber ibid; Rav Papa ibid as explains Rosh [unlike Rashi]; Elya Raba 32:59; See P”M 32 M”Z 33; Kol Yaakov 32:175; Biur Halacha ibid

[10] Admur ibid; Michaber ibid; Sefer Hateruma 209; Rosh Tefillin 9; Rambam Tefillin 3:2; Biur Halacha 32:39 “Sheyiyu in name of Shimusha Raba, Rif

Other opinions: Some Poskim rule that the Bayis is only required to have square corners and have equal diagonals, however it is not required to be an exact square of equal length and width, and hence could be a rectangle. [Ittur Hilchos Tefillin Shaar Harishon; Tosafus Menachos 35a “Some only make the Titura square”; Riaz beginning of Hilchos Tefillin in name of Tosafus Rid, brought in Shiltei Giborim on Rif in Hilchos Ketanos, Machazik Bracha 32, Zera Yaakov 2, and Rav Poalim 4:2; See Beis Yoseff 32:39; Poskim in Biur Halacha 32:39 “Sheyiyu”] Practically, he is a lone opinion on this subject and we do not rule this way. [Rav Poalim ibid] Others have a custom of making the top corners round [See M”A 32:53 who negates this custom]

[11] Admur ibid; Parentheses in original; See Chikrei Halachos 5:52

Other opinions: Some Poskim rule that only the corners of the Bayis must be square, and not the middle area. [Elya Raba 32 in name of Olas Tamid; See Piskeiy Teshuvos 32:60 footnote 418] Other Poskim rule it suffices for the Bayis to be square in majority of its length. [Chesed Leavraham 8]

[12] Admur ibid; Rama 32:39; Darkei Moshe 32 that so is custom; Beis Yosef 32 in name of Hagahos Ashri; Semag Asei 22; Sefer Hateruma end of Hilchos Tefillin 209; Rambam Tefillin 3:2

Other opinions: Some Poskim rule that initially one is to be particular that the height of the Bayis is equal to its width:length. [Darkei Moshe 32 in implication of Rambam; Eshkol; See Kol Yaakov 32:177]

[13] Admur ibid

Other opinions: Some Poskim rule that Bedieved, if the Bayis is not square, one may nevertheless wear the with a blessing. [Biur Halacha 32:39 “Sheyiyu” in name of Olas Tamid and Baruch Sheamar]

[14] Admur ibid; Michaber 32:39 in name of Yeish Mi Sheomer; Maharam 68; Beis Yosef 32 in name of Maharil, Teshuvah Ashkenazis; Rambam Tefillin 3, brought in M”B 32:173; This ruling applies according to all Poskim, and is not under dispute. [Machatzis Hashekel 32:54; Kol Yaakov 32:179]

[15] The reason: As the squareness of the Tefillin is a Halacha Lemoshe Misinai. [Admur ibid; Taz 32:34] It is hence not at all similar to Tzitzis, of which the law is that it remains Kosher even if some of its strings tear off. The reason for this is because by Tzitzis we have a special source to learn this from, as the verse states “Veasu Lahem Tzitzis” that only by the time of the making of the Tzitzis must it be whole. This does not apply to Tefillin. [Taz ibid; Beis Yosef 32]

[16] M”B 32:173; Biur Halacha 32:39 “Sheyihyu” in name of Yeshuos Yaakov; See Shevet Halevi3:2 that if the Tefillin are invalid according to all, then they are not to be worn at all

[17] Elya Raba 32:59 in name of Olas Tamid; Biur Halacha 32:39 “Sheyiyu” in name of Olas Tamid and Baruch Sheamar [that may even say a blessing!], Elya Raba, Yeshuos Yaakov

[18] Elya Raba 32:59 “As much as humanly possible, as its impossible to make an exact square.”; Madanei Yom Tov on Rosh; Maharsham 8:16; Peri Hasadeh 3:189; Os Chaim Veshalom 32:15; Eretz Tzevi 1:12; Igros Moshe 3:120; Mishneh Halachos 1:34; Piskeiy Teshuvos 32:62

[19] Under close measurement, even Mehudar Batim can be found to not be an exact square to the millimeter. Quite often there is at least a one-millimeter difference.

[20] Machatzis Hashekel 32:54; Kol Yaakov 32:181

Other opinions: Some write one is to check the corners one time every thirty days. [Orach Neman 32]

[21] Emek habracha 26 in name of Chazon Ish; Piskeiy Teshuvos 32:62

[22] M”B 32:177 in name of Beis Yosef; Tzitz Eliezer 13:6

Other opinions:

[23] Piskeiy Teshuvos 32 footnote 430

[24] Zichron Eliyahu 7:11;  Piskeiy Teshuvos 32:64

[25] M”B 32:174 although he concludes with a Tzaruch Iyun regarding Bedieved

[26] Piskeiy Teshuvos 32:62; See Keses Hasoofer 21:6

[27] See Piskeiy Teshuvos 32:62

[28] Birkeiy Yosef 32:12 in name of Beis Yehuda 3:88; Shaareiy Teshuvah 32:58; Zechor Leavraham Tefillin; Kol Yaakov 32:178; Od Yosef Chaiy Chayeh Sarah 9; See Maharsham 4:121; Tzafnas Paneiach 250; Piskeiy Teshuvos 32:62 footnote 435

[29] See Os Chaim Veshalom 32:15

[30] See Piskeiy Teshuvos 32:62

[31] Zichron Eliyahu 8; Sheivet Hakehasi 4:22

[32] Zicron Eliyahu 6:4; Piskeiy Teshuvos 33:1

[33] See Eretz Tzevi 1:11; Minchas Yitzchak 6:1; Piskeiy Teshuvos 32:60

[34] See Maharsham 4:121; Toras Chaim Sofer 32:92; Eretz Tzevi 12; Minchas Yitzchak 6:1; Shevet Halevi 3:2; 10:156; Divrei Yisrael 1:23; Piskeiy Teshuvos 32:63

[35] See Ashel Avraham Butchach 32; Daas Kedoshim 32:49-50; Piskeiy Teshuvos 32:63

[36] See Inside Stam p. 286

[37] Rav Poalim 4:2

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