in theory 11 yards. However material was always made in lengths of 9 yards, so she may just get the whole roll.
The dress pattern should give what is needed, for that particular pattern. Then multiply by 5.
2 196.04167 yards
Go to the link I have provided. Click on the type of pants you want, and scroll down to the yardages shown. There is a column heading at the top for size, follow that column to the width of the material (45" or 60") and you will see what the basic fabric amount is.
84 yards*45 inches/59 inches = 84 yards*45/59 = 64.07 yards (approx)
To convert tons to yards, you would need to know the specific material and its density. The conversion factor will vary depending on the material. Without this information, it is not possible to accurately convert tons to yards.
1.8 yards
When buying fabric for a dress it not only depends on the size, but also the style. What pattern are you using? Is 60 the pattern size or the persons regular dress size? Pattern sizing runs small and is typicaly 2 sizes away from you regular size in a store. For example I am a 28 on a pattern but a 24 when I buy clothes. There can be as much as a 30% difference in material used for knee length dress compared to a floor length dress. Are there sleves and if so how long. If using a plaid printed fabric you will need to add a few yards extra to match prints. I would buy at least 9 yards for size 60.
7 divided by 2 1/3 equals 3 Three skirts, each using 2 1/3 yards of material, can be made from 7 yards of material.
10/3 yards OR 3 and 1/3 yards OR 3.333333 yards
54 Inches = 1.50012 Yards
28 square feet = 3.1 square yards of material.
Approximate fabric in Lady Liberty's dress: 4000 sq. yards