The Frigidaire washer's user manual will specify the capacity of the unit. If you have the user manual, look for capacity information in the "use" or "features" sections of the manual. As a result of the age of the washer, the user manual is not readily available online, or through Frigidaire customer service.
To figure out the capacity, first measure the diameter of the tub. Use a tape measure to find the diameter, or the width of the tub in inches. Don't measure the entire width of the washer unit, or the diameter of the outer tub. Measure only the diameter of the inner tub, where the clothes are held.
The height of the tub is also needed to compute capacity. Measure the number of inches from the bottom of the tub to the top of it using the tape measure. Avoid measuring to the top of the washer unit. Only find the height of the inner portion of the tub where clothes are held.
Multiply the total width of the tub by pi, or 3.14. Then, multiply that answer by the total tub height. The result is the total capacity for the tub in cubic inches. Divide this number by 12 to determine the capacity in cubic feet. Frigidaire washers' have drum capacities that range from 2.65 to 3.68 cubic feet. If the total cubic feet of the tub is 3.5 or under, the washer has a medium sized capacity. Large capacity washers have a total volume of 3.6 to 4.2 cubic ft., and extra-large capacity washers start at 4.3 cubic ft.