I think I have heard that one should not measure or weigh things on Shabbat.

However, I wonder if this rule applies to Yom Tov related food needs, e.g., can one stick a food thermometer into meat to know if the meat is safe to eat or not, or measure flour for baking?

  • This source discusses the two problems which may apply to using a meat thermometer on Shabbos. But it doesn't discuss Yom Tov at all. Oct 18, 2019 at 19:45
  • I found a source which discusses measuring for the purpose of cooking on Yom Tov. ❧ In your case, the meat thermometer doesn't just help to ensure that the meat is cooked enough to taste good. In fact, it also helps to ensure that the meat is cooked enough to be safe to eat. So maybe the halacha is different. I dunno; I'm not a rabbi. Oct 18, 2019 at 20:00

2 Answers 2


Measuring precisely is forbidden on Yom Tov because it resembles mundane acts (uvdin d'chol). However some permit using measuring instruments (e.g., baking cups) if one uses them for approximate measures (some even permit if it is critical to the recipe and is done all the time). There are also exceptions for the sake of a mitzva (e.g., measuring a mikve or measures for one who has to eat on Yom Kippur) as these are not mundane acts.

It is also permitted to look at a thermometer, as such if the thermometer was of the type you put in the oven before Yom Tov, you can look at it, but inserting one in meat (if it even existed in a non-electric version) appears forbidden. See below for sources. and, of course, consult your rabbi before implementing anything you learn here.

R Yirmiyohu Kaganoff writes (under "Measuring")

In general, it is prohibited to measure on Yom Tov, just as it is prohibited to measure on Shabbos. Thus, one may not measure out how much flour, sugar, or oil to use in a recipe (Shulchan Aruch Orach Chayim 506:1). However, one may approximate how much flour, oil, or sugar is needed. It is permitted to use a measuring cup, as long as one does not fill the cup exactly to its measuring points (Mishnah Berurah 506:3).

The poskim dispute whether one may measure spices on Yom Tov, some permitting (even though it is prohibited to measure other items) because approximating spices may ruin the recipe if one errs (Beitzah 29a). However, Magen Avraham (504:10) contends that since most women cook without measuring spices on weekdays, but simply estimate how much they use, they may not measure spices on Yom Tov. Others contend that someone who measure spices on weekdays may measure them on Yom Tov.

R Moshe Lazarus at ohr writes

If baking on Yom Tov, it is forbidden to measure the flour if the precise amount is not critical, as in baking bread, because one could have measured it Erev Yom Tov. However, in baking cakes, etc., it may be done (Pri Megadim).

HalachaYomit (here and here) brings R Ovadia Yosef's rulings

For this reason, it is forbidden to weigh food items on a mechanical scale on Shabbat or Yom Tov. It is likewise forbidden to place liquids in special measuring cups in order to determine their weight or volume, for this constitutes measuring on Shabbat and Yom Tov.

Maran Rabbeinu Ovadia Yosef zt”l rules (in his Chazon Ovadia-Shabbat, Part 6, page 26, among other places) that on the night of the Pesach Seder, one may measure the Kezayit amounts of Matzah and Maror, for this is also considered measuring for the purpose of a Mitzvah and this does not resemble a mundane act.

It is nevertheless clear that although cooking on Yom Tov for the holiday meals is permissible and is a Mitzvah of enjoying and honoring the holiday, measuring or weighing food items for the purpose of cooking or baking is not considered measuring for the purpose of a Mitzvah, for only when something is completely recognizable as being done for the purpose of a Mitzvah, such as measuring Matzah and Maror or measuring a Mikveh, is this permissible. However, measuring for the purpose of cooking on Yom Tov is forbidden.

R Chaim Hillel Raskin at halacha.co writes

Chazal prohibited any form of measuring on Shabbos or on Yom Tov since it is a degradation of Shabbos and is similar to weekday activity, and also because it may cause a person to write. Some examples include: Measuring ingredients for a salad dressing, determining the size of a room (even just by counting the tiles), checking one’s weight or measuring height, or timing how long an activity takes. Only precise measuring is prohibited (even if later used in an imprecise manner), however approximate measuring (e.g. a cupful of baby cereal) is permissible.

Thus, when cooking on Yom Tov one should not measure the ingredients precisely, (measuring flour which can be done just the same before Yom Tov is not permitted even though cooking is permitted). However, spices may be measured if an imprecise amount will positively ruin the dish. [...]

Only actual measuring is prohibited. However, there is no prohibition to look at a clock or read the temperature from an already hanging thermostat.


Regarding your question whether you're allowed to use a meat thermometer on Yomtov, it seems that it is permitted. R' Moshe Feinstein writes (Igros Moshe 1, 128) that measuring one's temperature is not included in the gezeira of medida, i.e., measuring weight or volume of foods. He writes while it is praiseworthy to be stringent, one is not required to do so. Shemiras Shabbos Kehilchasa (the standard Halachic guide for Shabbos and Yomtov) in the name of R' Aurbach concurs with this view (40, footnote 3). Although they both deal specifically with measuring the temperature of humans, the logic applies to meat thermometers as well, as measuring of temps is not be included in the issur of medida.

Another point, according to SA (OC 504, 4) one may use a measuring device for spices since it is meant to prevent the overcooking and burning of the food. The above heter should be logically applied to meat thermometers as well, since the meat will be overcooked or undercooked without it, in such a case it should eb permitted (even if it were included in the issur of medida). This is the case even according to the mishna berura (ibid, 22), since people would generally use a meat thermometer on expensive meats during the week as well (it's just less common for people to eat expensive meats on common days).

For more sources on this, see here.

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