Chapter 90:12 & 13
12. It is forbidden on Shabbos to measure anything for a practical
purpose, unless doing so is required for the fulfillment of a mitzvah (1).
13. One may speak about one's business affairs either to a Jew or to a
Gentile on Shabbos, [only] if failing to do so would cause a [substantial]
(1) Measuring is one of the activities included in the general rabbinic
prohibition called "Uvdah De'Chol" ("weekday work").
Halacha-Yomi, Copyright (c) 2002 Project Genesis, Inc.