Casings come in a variety of sizes and are usually sold by the hank, bundle, cap or ounce. It is always difficult to estimate how much casing you will need to stuff your batch of sausage. A few rules of thumb:
1 pound of meat will stuff about 2 feet of medium-size hog casing (32-35 mm)
1 pound of meat will stuff about 4 feet of medium-size lamb casing (20-22 mm)
1 ounce of medium-size hog casing (32-35 mm) will stuff about 8 feet of sausage
1 pound of medium-size lamb casing (20-22 mm) will stuff about 16 feet of sausage
The above table also gives some useful casing information
hope that you find this of some use
kind regards
Parson Snows