Measuring the right size of water-soluble, biodegradable bags is easy. First, measure the area where you will be placing the bag. If you need to fit items into the bag, be sure to factor in their sizes as well. Once you have determined the approximate size for your bag, compare it against pre-made water-soluble biodegradable bags to find one that is closest in size. If a pre-made option isn’t available, custom sizes can also be ordered from most suppliers.