The rollout method works. If you don't have a metric tape measure, you can use google to convert it.

For instance, entering 83 1/8 inches in mm in google search, you get this answer:

(83 1/8) inches = 2 111.375 millimeters

google will convert a lot of units. 4 lbs in grams returns: 4 pounds = 1 814.36948 grams