Convert from uncia [Rome] to petagram

Unit Definition (uncia [Rome])
The uncia is the Roman ounce, equal to about 27.2875 grams of 0.9625 ounce avoirdupois. There were 12 ounces in a Roman pound, and the word uncia means a 12th part; its name gives us the ounce, of course, and also the inch.

Unit Definition (petagram)
The petagram is a metric unit of mass equal to 10E15 grams or 1 gigatonne (one billion metric tons). This unit is used in atmospheric science and other scientific contexts where large masses are considered.