Chapter 29
Laws Derived from Isaiah: Running, Walking, Commerce, Measuring, Reading, Speaking
MEASURING AND WEIGHING ON SHABBATH AND YOM TOV
40.a. One may weigh or measure baby food, if one has to know how much the baby eats.
40.b. However, if possible, one should estimate the quantity rather than measure it exactly. (See paragraph 34 above.)
41.a. When preparing food on Yom Tov, one may use a marked measuring cup, in order to ascertain the quantities of the various spices and flavorings one is using, provided that
1) the taste of the food would be adversely affected if one were to use inexact quantities and
2) one would normally measure these ingredients if preparing the food on another day.
41.b. Nevertheless, one should not use scales to weigh the ingredients.

